diff --git a/README.md b/README.md
index 195daf598..32eaa84a7 100644
--- a/README.md
+++ b/README.md
@@ -54,9 +54,18 @@ LeetCode Problems' Solutions
| # | Title | Solution | Difficulty |
| :-: | - | - | :-: |
+| 1187 | [Make Array Strictly Increasing](https://leetcode.com/problems/make-array-strictly-increasing "使数组严格递增") | [Go](https://github.com/openset/leetcode/tree/master/problems/make-array-strictly-increasing) | Hard |
+| 1186 | [Maximum Subarray Sum with One Deletion](https://leetcode.com/problems/maximum-subarray-sum-with-one-deletion "删除一次得到子数组最大和") | [Go](https://github.com/openset/leetcode/tree/master/problems/maximum-subarray-sum-with-one-deletion) | Medium |
+| 1185 | [Day of the Week](https://leetcode.com/problems/day-of-the-week "一周中的第几天") | [Go](https://github.com/openset/leetcode/tree/master/problems/day-of-the-week) | Easy |
+| 1184 | [Distance Between Bus Stops](https://leetcode.com/problems/distance-between-bus-stops "公交站间的距离") | [Go](https://github.com/openset/leetcode/tree/master/problems/distance-between-bus-stops) | Easy |
+| 1183 | [Maximum Number of Ones](https://leetcode.com/problems/maximum-number-of-ones "矩阵中 1 的最大数量") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/maximum-number-of-ones) | Hard |
+| 1182 | [Shortest Distance to Target Color](https://leetcode.com/problems/shortest-distance-to-target-color "与目标颜色间的最短距离") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/shortest-distance-to-target-color) | Medium |
+| 1181 | [Before and After Puzzle](https://leetcode.com/problems/before-and-after-puzzle "前后拼接") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/before-and-after-puzzle) | Medium |
+| 1180 | [Count Substrings with Only One Distinct Letter](https://leetcode.com/problems/count-substrings-with-only-one-distinct-letter "统计只含单一字母的子串") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/count-substrings-with-only-one-distinct-letter) | Easy |
+| 1179 | [Reformat Department Table](https://leetcode.com/problems/reformat-department-table) | [MySQL](https://github.com/openset/leetcode/tree/master/problems/reformat-department-table) | Easy |
| 1178 | [Number of Valid Words for Each Puzzle](https://leetcode.com/problems/number-of-valid-words-for-each-puzzle "猜字谜") | [Go](https://github.com/openset/leetcode/tree/master/problems/number-of-valid-words-for-each-puzzle) | Hard |
| 1177 | [Can Make Palindrome from Substring](https://leetcode.com/problems/can-make-palindrome-from-substring "构建回文串检测") | [Go](https://github.com/openset/leetcode/tree/master/problems/can-make-palindrome-from-substring) | Medium |
-| 1176 | [Diet Plan Performance](https://leetcode.com/problems/diet-plan-performance "健身计划评估") | [Go](https://github.com/openset/leetcode/tree/master/problems/diet-plan-performance) | Easy |
+| 1176 | [Diet Plan Performance](https://leetcode.com/problems/diet-plan-performance "健身计划评估") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/diet-plan-performance) | Easy |
| 1175 | [Prime Arrangements](https://leetcode.com/problems/prime-arrangements "质数排列") | [Go](https://github.com/openset/leetcode/tree/master/problems/prime-arrangements) | Easy |
| 1174 | [Immediate Food Delivery II](https://leetcode.com/problems/immediate-food-delivery-ii) 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/immediate-food-delivery-ii) | Medium |
| 1173 | [Immediate Food Delivery I](https://leetcode.com/problems/immediate-food-delivery-i) 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/immediate-food-delivery-i) | Easy |
@@ -157,14 +166,14 @@ LeetCode Problems' Solutions
| 1078 | [Occurrences After Bigram](https://leetcode.com/problems/occurrences-after-bigram "Bigram 分词") | [Go](https://github.com/openset/leetcode/tree/master/problems/occurrences-after-bigram) | Easy |
| 1077 | [Project Employees III](https://leetcode.com/problems/project-employees-iii "项目员工 III") 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/project-employees-iii) | Medium |
| 1076 | [Project Employees II](https://leetcode.com/problems/project-employees-ii) 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/project-employees-ii) | Easy |
-| 1075 | [Project Employees I](https://leetcode.com/problems/project-employees-i) 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/project-employees-i) | Easy |
+| 1075 | [Project Employees I](https://leetcode.com/problems/project-employees-i "项目员工 I") 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/project-employees-i) | Easy |
| 1074 | [Number of Submatrices That Sum to Target](https://leetcode.com/problems/number-of-submatrices-that-sum-to-target "元素和为目标值的子矩阵数量") | [Go](https://github.com/openset/leetcode/tree/master/problems/number-of-submatrices-that-sum-to-target) | Hard |
| 1073 | [Adding Two Negabinary Numbers](https://leetcode.com/problems/adding-two-negabinary-numbers "负二进制数相加") | [Go](https://github.com/openset/leetcode/tree/master/problems/adding-two-negabinary-numbers) | Medium |
| 1072 | [Flip Columns For Maximum Number of Equal Rows](https://leetcode.com/problems/flip-columns-for-maximum-number-of-equal-rows "按列翻转得到最大值等行数") | [Go](https://github.com/openset/leetcode/tree/master/problems/flip-columns-for-maximum-number-of-equal-rows) | Medium |
| 1071 | [Greatest Common Divisor of Strings](https://leetcode.com/problems/greatest-common-divisor-of-strings "字符串的最大公因子") | [Go](https://github.com/openset/leetcode/tree/master/problems/greatest-common-divisor-of-strings) | Easy |
| 1070 | [Product Sales Analysis III](https://leetcode.com/problems/product-sales-analysis-iii) 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/product-sales-analysis-iii) | Medium |
| 1069 | [Product Sales Analysis II](https://leetcode.com/problems/product-sales-analysis-ii "产品销售分析 II") 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/product-sales-analysis-ii) | Easy |
-| 1068 | [Product Sales Analysis I](https://leetcode.com/problems/product-sales-analysis-i) 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/product-sales-analysis-i) | Easy |
+| 1068 | [Product Sales Analysis I](https://leetcode.com/problems/product-sales-analysis-i "产品销售分析 I") 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/product-sales-analysis-i) | Easy |
| 1067 | [Digit Count in Range](https://leetcode.com/problems/digit-count-in-range "范围内的数字计数") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/digit-count-in-range) | Hard |
| 1066 | [Campus Bikes II](https://leetcode.com/problems/campus-bikes-ii "校园自行车分配 II") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/campus-bikes-ii) | Medium |
| 1065 | [Index Pairs of a String](https://leetcode.com/problems/index-pairs-of-a-string "字符串的索引对") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/index-pairs-of-a-string) | Easy |
@@ -295,7 +304,7 @@ LeetCode Problems' Solutions
| 940 | [Distinct Subsequences II](https://leetcode.com/problems/distinct-subsequences-ii "不同的子序列 II") | [Go](https://github.com/openset/leetcode/tree/master/problems/distinct-subsequences-ii) | Hard |
| 939 | [Minimum Area Rectangle](https://leetcode.com/problems/minimum-area-rectangle "最小面积矩形") | [Go](https://github.com/openset/leetcode/tree/master/problems/minimum-area-rectangle) | Medium |
| 938 | [Range Sum of BST](https://leetcode.com/problems/range-sum-of-bst "二叉搜索树的范围和") | [Go](https://github.com/openset/leetcode/tree/master/problems/range-sum-of-bst) | Easy |
-| 937 | [Reorder Log Files](https://leetcode.com/problems/reorder-log-files "重新排列日志文件") | [Go](https://github.com/openset/leetcode/tree/master/problems/reorder-log-files) | Easy |
+| 937 | [Reorder Data in Log Files](https://leetcode.com/problems/reorder-data-in-log-files "重新排列日志文件") | [Go](https://github.com/openset/leetcode/tree/master/problems/reorder-data-in-log-files) | Easy |
| 936 | [Stamping The Sequence](https://leetcode.com/problems/stamping-the-sequence "戳印序列") | [Go](https://github.com/openset/leetcode/tree/master/problems/stamping-the-sequence) | Hard |
| 935 | [Knight Dialer](https://leetcode.com/problems/knight-dialer "骑士拨号器") | [Go](https://github.com/openset/leetcode/tree/master/problems/knight-dialer) | Medium |
| 934 | [Shortest Bridge](https://leetcode.com/problems/shortest-bridge "最短的桥") | [Go](https://github.com/openset/leetcode/tree/master/problems/shortest-bridge) | Medium |
diff --git a/problems/before-and-after-puzzle/README.md b/problems/before-and-after-puzzle/README.md
new file mode 100644
index 000000000..41198589f
--- /dev/null
+++ b/problems/before-and-after-puzzle/README.md
@@ -0,0 +1,28 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/count-substrings-with-only-one-distinct-letter "Count Substrings with Only One Distinct Letter")
+
+[Next >](https://github.com/openset/leetcode/tree/master/problems/shortest-distance-to-target-color "Shortest Distance to Target Color")
+
+## 1181. Before and After Puzzle (Medium)
+
+
+
+### Related Topics
+ [[String](https://github.com/openset/leetcode/tree/master/tag/string/README.md)]
+
+### Hints
+
+Hint 1
+What if you check every pair of strings (bruteforce)?
+
+
+
+Hint 2
+For every two strings, check if they can form a puzzle by comparing their last and first words.
+
diff --git a/problems/best-time-to-buy-and-sell-stock-ii/README.md b/problems/best-time-to-buy-and-sell-stock-ii/README.md
index 4257b8cc1..a379f0e32 100644
--- a/problems/best-time-to-buy-and-sell-stock-ii/README.md
+++ b/problems/best-time-to-buy-and-sell-stock-ii/README.md
@@ -44,8 +44,8 @@
Explanation: In this case, no transaction is done, i.e. max profit = 0.
### Related Topics
- [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
[[Greedy](https://github.com/openset/leetcode/tree/master/tag/greedy/README.md)]
+ [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
### Similar Questions
1. [Best Time to Buy and Sell Stock](https://github.com/openset/leetcode/tree/master/problems/best-time-to-buy-and-sell-stock) (Easy)
diff --git a/problems/can-make-palindrome-from-substring/README.md b/problems/can-make-palindrome-from-substring/README.md
index 054f2c79c..44eabf9bf 100644
--- a/problems/can-make-palindrome-from-substring/README.md
+++ b/problems/can-make-palindrome-from-substring/README.md
@@ -9,7 +9,7 @@
[Next >](https://github.com/openset/leetcode/tree/master/problems/number-of-valid-words-for-each-puzzle "Number of Valid Words for Each Puzzle")
-## 5175. Can Make Palindrome from Substring (Medium)
+## 1177. Can Make Palindrome from Substring (Medium)
Given a string s, we make queries on substrings of s.
diff --git a/problems/count-substrings-with-only-one-distinct-letter/README.md b/problems/count-substrings-with-only-one-distinct-letter/README.md
new file mode 100644
index 000000000..a17c039e6
--- /dev/null
+++ b/problems/count-substrings-with-only-one-distinct-letter/README.md
@@ -0,0 +1,34 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/reformat-department-table "Reformat Department Table")
+
+[Next >](https://github.com/openset/leetcode/tree/master/problems/before-and-after-puzzle "Before and After Puzzle")
+
+## 1180. Count Substrings with Only One Distinct Letter (Easy)
+
+
+
+### Related Topics
+ [[Math](https://github.com/openset/leetcode/tree/master/tag/math/README.md)]
+ [[String](https://github.com/openset/leetcode/tree/master/tag/string/README.md)]
+
+### Hints
+
+Hint 1
+What if we divide the string into substrings containing only one distinct character with maximal lengths?
+
+
+
+Hint 2
+Now that you have sub-strings with only one distinct character, Try to come up with a formula that counts the number of its sub-strings.
+
+
+
+Hint 3
+Alternatively, Observe that the constraints are small so you can use brute force.
+
diff --git a/problems/day-of-the-week/README.md b/problems/day-of-the-week/README.md
new file mode 100644
index 000000000..370666eee
--- /dev/null
+++ b/problems/day-of-the-week/README.md
@@ -0,0 +1,66 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/distance-between-bus-stops "Distance Between Bus Stops")
+
+[Next >](https://github.com/openset/leetcode/tree/master/problems/maximum-subarray-sum-with-one-deletion "Maximum Subarray Sum with One Deletion")
+
+## 1185. Day of the Week (Easy)
+
+Given a date, return the corresponding day of the week for that date.
+
+The input is given as three integers representing the day, month and year respectively.
+
+Return the answer as one of the following values {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"}.
+
+
+Example 1:
+
+
+Input: day = 31, month = 8, year = 2019
+Output: "Saturday"
+
+
+Example 2:
+
+
+Input: day = 18, month = 7, year = 1999
+Output: "Sunday"
+
+
+Example 3:
+
+
+Input: day = 15, month = 8, year = 1993
+Output: "Sunday"
+
+
+
+Constraints:
+
+
+ - The given dates are valid dates between the years
1971 and 2100.
+
+
+### Related Topics
+ [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
+
+### Hints
+
+Hint 1
+Sum up the number of days for the years before the given year.
+
+
+
+Hint 2
+Handle the case of a leap year.
+
+
+
+Hint 3
+Find the number of days for each month of the given year.
+
diff --git a/problems/diet-plan-performance/README.md b/problems/diet-plan-performance/README.md
index 26421deaf..7d81903c3 100644
--- a/problems/diet-plan-performance/README.md
+++ b/problems/diet-plan-performance/README.md
@@ -9,7 +9,7 @@
[Next >](https://github.com/openset/leetcode/tree/master/problems/can-make-palindrome-from-substring "Can Make Palindrome from Substring")
-## 5174. Diet Plan Performance (Easy)
+## 1176. Diet Plan Performance (Easy)
A dieter consumes calories[i] calories on the i-th day. For every consecutive sequence of k days, they look at T, the total calories consumed during that sequence of k days:
@@ -44,7 +44,7 @@
Input: calories = [6,5,0,0], k = 2, lower = 1, upper = 5
Output: 0
-Explaination: calories[0] + calories[1] > upper, calories[2] + calories[3] < lower, total points = 0.
+Explaination: calories[0] + calories[1] > upper, lower <= calories[1] + calories[2] <= upper, calories[2] + calories[3] < lower, total points = 0.
diff --git a/problems/distance-between-bus-stops/README.md b/problems/distance-between-bus-stops/README.md
new file mode 100644
index 000000000..9adde3bd9
--- /dev/null
+++ b/problems/distance-between-bus-stops/README.md
@@ -0,0 +1,71 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/maximum-number-of-ones "Maximum Number of Ones")
+
+[Next >](https://github.com/openset/leetcode/tree/master/problems/day-of-the-week "Day of the Week")
+
+## 1184. Distance Between Bus Stops (Easy)
+
+A bus has n stops numbered from 0 to n - 1 that form a circle. We know the distance between all pairs of neighboring stops where distance[i] is the distance between the stops number i and (i + 1) % n.
+
+The bus goes along both directions i.e. clockwise and counterclockwise.
+
+Return the shortest distance between the given start and destination stops.
+
+
+Example 1:
+
+
+
+
+Input: distance = [1,2,3,4], start = 0, destination = 1
+Output: 1
+Explanation: Distance between 0 and 1 is 1 or 9, minimum is 1.
+
+
+
+Example 2:
+
+
+
+
+Input: distance = [1,2,3,4], start = 0, destination = 2
+Output: 3
+Explanation: Distance between 0 and 2 is 3 or 7, minimum is 3.
+
+
+
+
+Example 3:
+
+
+
+
+Input: distance = [1,2,3,4], start = 0, destination = 3
+Output: 4
+Explanation: Distance between 0 and 3 is 6 or 4, minimum is 4.
+
+
+
+Constraints:
+
+
+ 1 <= n <= 10^4distance.length == n0 <= start, destination < n0 <= distance[i] <= 10^4
+
+### Related Topics
+ [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
+
+### Hints
+
+Hint 1
+Find the distance between the two stops if the bus moved in clockwise or counterclockwise directions.
+
diff --git a/problems/insertion-sort-list/README.md b/problems/insertion-sort-list/README.md
index 72eff798a..ccb768d9d 100644
--- a/problems/insertion-sort-list/README.md
+++ b/problems/insertion-sort-list/README.md
@@ -48,8 +48,8 @@ With each iteration one element (red) is removed from the input data and inserte
### Related Topics
- [[Linked List](https://github.com/openset/leetcode/tree/master/tag/linked-list/README.md)]
[[Sort](https://github.com/openset/leetcode/tree/master/tag/sort/README.md)]
+ [[Linked List](https://github.com/openset/leetcode/tree/master/tag/linked-list/README.md)]
### Similar Questions
1. [Sort List](https://github.com/openset/leetcode/tree/master/problems/sort-list) (Medium)
diff --git a/problems/longest-consecutive-sequence/README.md b/problems/longest-consecutive-sequence/README.md
index 257addc45..43b0bd141 100644
--- a/problems/longest-consecutive-sequence/README.md
+++ b/problems/longest-consecutive-sequence/README.md
@@ -24,8 +24,8 @@
### Related Topics
- [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
[[Union Find](https://github.com/openset/leetcode/tree/master/tag/union-find/README.md)]
+ [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
### Similar Questions
1. [Binary Tree Longest Consecutive Sequence](https://github.com/openset/leetcode/tree/master/problems/binary-tree-longest-consecutive-sequence) (Medium)
diff --git a/problems/majority-element/README.md b/problems/majority-element/README.md
index f274178fa..8f50acbf8 100644
--- a/problems/majority-element/README.md
+++ b/problems/majority-element/README.md
@@ -29,9 +29,9 @@
### Related Topics
+ [[Bit Manipulation](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)]
[[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
[[Divide and Conquer](https://github.com/openset/leetcode/tree/master/tag/divide-and-conquer/README.md)]
- [[Bit Manipulation](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)]
### Similar Questions
1. [Majority Element II](https://github.com/openset/leetcode/tree/master/problems/majority-element-ii) (Medium)
diff --git a/problems/make-array-strictly-increasing/README.md b/problems/make-array-strictly-increasing/README.md
new file mode 100644
index 000000000..3031267a9
--- /dev/null
+++ b/problems/make-array-strictly-increasing/README.md
@@ -0,0 +1,66 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/maximum-subarray-sum-with-one-deletion "Maximum Subarray Sum with One Deletion")
+
+Next >
+
+## 1187. Make Array Strictly Increasing (Hard)
+
+Given two integer arrays arr1 and arr2, return the minimum number of operations (possibly zero) needed to make arr1 strictly increasing.
+
+In one operation, you can choose two indices 0 <= i < arr1.length and 0 <= j < arr2.length and do the assignment arr1[i] = arr2[j].
+
+If there is no way to make arr1 strictly increasing, return -1.
+
+
+Example 1:
+
+
+Input: arr1 = [1,5,3,6,7], arr2 = [1,3,2,4]
+Output: 1
+Explanation: Replace 5 with 2, then arr1 = [1, 2, 3, 6, 7].
+
+
+Example 2:
+
+
+Input: arr1 = [1,5,3,6,7], arr2 = [4,3,1]
+Output: 2
+Explanation: Replace 5 with 3 and then replace 3 with 4. arr1 = [1, 3, 4, 6, 7].
+
+
+Example 3:
+
+
+Input: arr1 = [1,5,3,6,7], arr2 = [1,6,3,3]
+Output: -1
+Explanation: You can't make arr1 strictly increasing.
+
+
+Constraints:
+
+
+ 1 <= arr1.length, arr2.length <= 20000 <= arr1[i], arr2[i] <= 10^9
+
+
+
+### Related Topics
+ [[Dynamic Programming](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)]
+
+### Hints
+
+Hint 1
+Use dynamic programming.
+
+
+
+Hint 2
+The state would be the index in arr1 and the index of the previous element in arr2 after sorting it and removing duplicates.
+
diff --git a/problems/maximum-number-of-ones/README.md b/problems/maximum-number-of-ones/README.md
new file mode 100644
index 000000000..60c4ff839
--- /dev/null
+++ b/problems/maximum-number-of-ones/README.md
@@ -0,0 +1,39 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/shortest-distance-to-target-color "Shortest Distance to Target Color")
+
+[Next >](https://github.com/openset/leetcode/tree/master/problems/distance-between-bus-stops "Distance Between Bus Stops")
+
+## 1183. Maximum Number of Ones (Hard)
+
+
+
+### Related Topics
+ [[Math](https://github.com/openset/leetcode/tree/master/tag/math/README.md)]
+ [[Sort](https://github.com/openset/leetcode/tree/master/tag/sort/README.md)]
+
+### Hints
+
+Hint 1
+Think of a greedy mathematical solution.
+
+
+
+Hint 2
+Say you choose to set some cell (i, j) to 1, all cells (x, y) such that i % sideLength == x % sideLength and j % sideLength == y % sideLength can also be set to 1 without increasing the max number of ones in a sub-matrix.
+
+
+
+Hint 3
+In one move, choose to set all the cells with some modulus (i % sideLength, j % sideLength) to 1.
+
+
+
+Hint 4
+Choose the cells with max frequency.
+
diff --git a/problems/maximum-subarray-sum-with-one-deletion/README.md b/problems/maximum-subarray-sum-with-one-deletion/README.md
new file mode 100644
index 000000000..9bdd7636f
--- /dev/null
+++ b/problems/maximum-subarray-sum-with-one-deletion/README.md
@@ -0,0 +1,67 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/day-of-the-week "Day of the Week")
+
+[Next >](https://github.com/openset/leetcode/tree/master/problems/make-array-strictly-increasing "Make Array Strictly Increasing")
+
+## 1186. Maximum Subarray Sum with One Deletion (Medium)
+
+Given an array of integers, return the maximum sum for a non-empty subarray (contiguous elements) with at most one element deletion. In other words, you want to choose a subarray and optionally delete one element from it so that there is still at least one element left and the sum of the remaining elements is maximum possible.
+
+Note that the subarray needs to be non-empty after deleting one element.
+
+
+Example 1:
+
+
+Input: arr = [1,-2,0,3]
+Output: 4
+Explanation: Because we can choose [1, -2, 0, 3] and drop -2, thus the subarray [1, 0, 3] becomes the maximum value.
+
+Example 2:
+
+
+Input: arr = [1,-2,-2,3]
+Output: 3
+Explanation: We just choose [3] and it's the maximum sum.
+
+
+Example 3:
+
+
+Input: arr = [-1,-1,-1,-1]
+Output: -1
+Explanation: The final subarray needs to be non-empty. You can't choose [-1] and delete -1 from it, then get an empty subarray to make the sum equals to 0.
+
+
+
+Constraints:
+
+
+ 1 <= arr.length <= 10^5-10^4 <= arr[i] <= 10^4
+
+### Related Topics
+ [[Dynamic Programming](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)]
+
+### Hints
+
+Hint 1
+How to solve this problem if no deletions are allowed ?
+
+
+
+Hint 2
+Try deleting each element and find the maximum subarray sum to both sides of that element.
+
+
+
+Hint 3
+To do that efficiently, use the idea of Kadane's algorithm.
+
diff --git a/problems/number-of-valid-words-for-each-puzzle/README.md b/problems/number-of-valid-words-for-each-puzzle/README.md
index 3026be55d..8b5e49eee 100644
--- a/problems/number-of-valid-words-for-each-puzzle/README.md
+++ b/problems/number-of-valid-words-for-each-puzzle/README.md
@@ -7,9 +7,9 @@
[< Previous](https://github.com/openset/leetcode/tree/master/problems/can-make-palindrome-from-substring "Can Make Palindrome from Substring")
-Next >
+[Next >](https://github.com/openset/leetcode/tree/master/problems/reformat-department-table "Reformat Department Table")
-## 5176. Number of Valid Words for Each Puzzle (Hard)
+## 1178. Number of Valid Words for Each Puzzle (Hard)
With respect to a given puzzle string, a word is valid if both the following conditions are satisfied:
++---------------+---------+
+| Column Name | Type |
++---------------+---------+
+| id | int |
+| revenue | int |
+| month | varchar |
++---------------+---------+
+(id, month) is the primary key of this table.
+The table has information about the revenue of each department per month.
+The month has values in ["Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"].
+
+
+
+
+Write an SQL query to reformat the table such that there is a department id column and a revenue column for each month.
+
+The query result format is in the following example:
+
+
+Department table:
++------+---------+-------+
+| id | revenue | month |
++------+---------+-------+
+| 1 | 8000 | Jan |
+| 2 | 9000 | Jan |
+| 3 | 10000 | Feb |
+| 1 | 7000 | Feb |
+| 1 | 6000 | Mar |
++------+---------+-------+
+
+Result table:
++------+-------------+-------------+-------------+-----+-------------+
+| id | Jan_Revenue | Feb_Revenue | Mar_Revenue | ... | Dec_Revenue |
++------+-------------+-------------+-------------+-----+-------------+
+| 1 | 8000 | 7000 | 6000 | ... | null |
+| 2 | 9000 | null | null | ... | null |
+| 3 | null | 10000 | null | ... | null |
++------+-------------+-------------+-------------+-----+-------------+
+
+Note that the result table has 13 columns (1 for the department id + 12 for the months).
+
diff --git a/problems/reformat-department-table/mysql_schemas.sql b/problems/reformat-department-table/mysql_schemas.sql
new file mode 100644
index 000000000..1c652dfcf
--- /dev/null
+++ b/problems/reformat-department-table/mysql_schemas.sql
@@ -0,0 +1,7 @@
+Create table If Not Exists Department (id int, revenue int, month varchar(5));
+Truncate table Department;
+insert into Department (id, revenue, month) values ('1', '8000', 'Jan');
+insert into Department (id, revenue, month) values ('2', '9000', 'Jan');
+insert into Department (id, revenue, month) values ('3', '10000', 'Feb');
+insert into Department (id, revenue, month) values ('1', '7000', 'Feb');
+insert into Department (id, revenue, month) values ('1', '6000', 'Mar');
diff --git a/problems/reorder-data-in-log-files/README.md b/problems/reorder-data-in-log-files/README.md
new file mode 100644
index 000000000..5602e156a
--- /dev/null
+++ b/problems/reorder-data-in-log-files/README.md
@@ -0,0 +1,44 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/stamping-the-sequence "Stamping The Sequence")
+
+[Next >](https://github.com/openset/leetcode/tree/master/problems/range-sum-of-bst "Range Sum of BST")
+
+## 937. Reorder Data in Log Files (Easy)
+
+You have an array of logs. Each log is a space delimited string of words.
+
+For each log, the first word in each log is an alphanumeric identifier. Then, either:
+
+
+ - Each word after the identifier will consist only of lowercase letters, or;
+ - Each word after the identifier will consist only of digits.
+
+
+We will call these two varieties of logs letter-logs and digit-logs. It is guaranteed that each log has at least one word after its identifier.
+
+Reorder the logs so that all of the letter-logs come before any digit-log. The letter-logs are ordered lexicographically ignoring identifier, with the identifier used in case of ties. The digit-logs should be put in their original order.
+
+Return the final order of the logs.
+
+
+Example 1:
+Input: logs = ["dig1 8 1 5 1","let1 art can","dig2 3 6","let2 own kit dig","let3 art zero"]
+Output: ["let1 art can","let3 art zero","let2 own kit dig","dig1 8 1 5 1","dig2 3 6"]
+
+
+Constraints:
+
+
+ 0 <= logs.length <= 1003 <= logs[i].length <= 100logs[i] is guaranteed to have an identifier, and a word after the identifier.
+
+### Related Topics
+ [[String](https://github.com/openset/leetcode/tree/master/tag/string/README.md)]
diff --git a/problems/shortest-distance-to-target-color/README.md b/problems/shortest-distance-to-target-color/README.md
new file mode 100644
index 000000000..39948a7d4
--- /dev/null
+++ b/problems/shortest-distance-to-target-color/README.md
@@ -0,0 +1,33 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/before-and-after-puzzle "Before and After Puzzle")
+
+[Next >](https://github.com/openset/leetcode/tree/master/problems/maximum-number-of-ones "Maximum Number of Ones")
+
+## 1182. Shortest Distance to Target Color (Medium)
+
+
+
+### Related Topics
+ [[Binary Search](https://github.com/openset/leetcode/tree/master/tag/binary-search/README.md)]
+
+### Hints
+
+Hint 1
+Greedy solution is too slow because of the limits.
+
+
+
+Hint 2
+Can you solve this problem offline by doing some pre-processing?
+
+
+
+Hint 3
+Calculate the answers for all indexes moving to their left and to their right.
+
diff --git a/problems/single-number/README.md b/problems/single-number/README.md
index a7d7c6213..c802f21c5 100644
--- a/problems/single-number/README.md
+++ b/problems/single-number/README.md
@@ -32,8 +32,8 @@
### Related Topics
- [[Hash Table](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)]
[[Bit Manipulation](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)]
+ [[Hash Table](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)]
### Similar Questions
1. [Single Number II](https://github.com/openset/leetcode/tree/master/problems/single-number-ii) (Medium)
diff --git a/problems/sort-list/README.md b/problems/sort-list/README.md
index 22cf9683f..46456c7b3 100644
--- a/problems/sort-list/README.md
+++ b/problems/sort-list/README.md
@@ -27,8 +27,8 @@
Output: -1->0->3->4->5
### Related Topics
- [[Linked List](https://github.com/openset/leetcode/tree/master/tag/linked-list/README.md)]
[[Sort](https://github.com/openset/leetcode/tree/master/tag/sort/README.md)]
+ [[Linked List](https://github.com/openset/leetcode/tree/master/tag/linked-list/README.md)]
### Similar Questions
1. [Merge Two Sorted Lists](https://github.com/openset/leetcode/tree/master/problems/merge-two-sorted-lists) (Easy)
diff --git a/problems/stamping-the-sequence/README.md b/problems/stamping-the-sequence/README.md
index 7180fe414..847ac5d5e 100644
--- a/problems/stamping-the-sequence/README.md
+++ b/problems/stamping-the-sequence/README.md
@@ -7,7 +7,7 @@
[< Previous](https://github.com/openset/leetcode/tree/master/problems/knight-dialer "Knight Dialer")
-[Next >](https://github.com/openset/leetcode/tree/master/problems/reorder-log-files "Reorder Log Files")
+[Next >](https://github.com/openset/leetcode/tree/master/problems/reorder-data-in-log-files "Reorder Data in Log Files")
## 936. Stamping The Sequence (Hard)
diff --git a/problems/two-sum-iii-data-structure-design/README.md b/problems/two-sum-iii-data-structure-design/README.md
index e4a53a3f4..3f8f33cc8 100644
--- a/problems/two-sum-iii-data-structure-design/README.md
+++ b/problems/two-sum-iii-data-structure-design/README.md
@@ -14,8 +14,8 @@
### Related Topics
- [[Hash Table](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)]
[[Design](https://github.com/openset/leetcode/tree/master/tag/design/README.md)]
+ [[Hash Table](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)]
### Similar Questions
1. [Two Sum](https://github.com/openset/leetcode/tree/master/problems/two-sum) (Easy)
diff --git a/problems/word-ladder-ii/README.md b/problems/word-ladder-ii/README.md
index 4335d1576..445628286 100644
--- a/problems/word-ladder-ii/README.md
+++ b/problems/word-ladder-ii/README.md
@@ -60,10 +60,10 @@ wordList = ["hot","dot","dog","lot",&quo
### Related Topics
+ [[Breadth-first Search](https://github.com/openset/leetcode/tree/master/tag/breadth-first-search/README.md)]
[[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
[[String](https://github.com/openset/leetcode/tree/master/tag/string/README.md)]
[[Backtracking](https://github.com/openset/leetcode/tree/master/tag/backtracking/README.md)]
- [[Breadth-first Search](https://github.com/openset/leetcode/tree/master/tag/breadth-first-search/README.md)]
### Similar Questions
1. [Word Ladder](https://github.com/openset/leetcode/tree/master/problems/word-ladder) (Medium)
diff --git a/readme/301-600.md b/readme/301-600.md
index d53acd694..d9fa46624 100644
--- a/readme/301-600.md
+++ b/readme/301-600.md
@@ -264,7 +264,7 @@ LeetCode Problems' Solutions
| 508 | [Most Frequent Subtree Sum](https://leetcode.com/problems/most-frequent-subtree-sum "出现次数最多的子树元素和") | [Go](https://github.com/openset/leetcode/tree/master/problems/most-frequent-subtree-sum) | Medium |
| 509 | [Fibonacci Number](https://leetcode.com/problems/fibonacci-number "斐波那契数") | [Go](https://github.com/openset/leetcode/tree/master/problems/fibonacci-number) | Easy |
| 510 | [Inorder Successor in BST II](https://leetcode.com/problems/inorder-successor-in-bst-ii "二叉搜索树中的中序后继 II") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/inorder-successor-in-bst-ii) | Medium |
-| 511 | [Game Play Analysis I](https://leetcode.com/problems/game-play-analysis-i) 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/game-play-analysis-i) | Easy |
+| 511 | [Game Play Analysis I](https://leetcode.com/problems/game-play-analysis-i "游戏玩法分析 I") 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/game-play-analysis-i) | Easy |
| 512 | [Game Play Analysis II](https://leetcode.com/problems/game-play-analysis-ii) 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/game-play-analysis-ii) | Easy |
| 513 | [Find Bottom Left Tree Value](https://leetcode.com/problems/find-bottom-left-tree-value "找树左下角的值") | [Go](https://github.com/openset/leetcode/tree/master/problems/find-bottom-left-tree-value) | Medium |
| 514 | [Freedom Trail](https://leetcode.com/problems/freedom-trail "自由之路") | [Go](https://github.com/openset/leetcode/tree/master/problems/freedom-trail) | Hard |
diff --git a/tag/array/README.md b/tag/array/README.md
index 39274b492..c795b9fb2 100644
--- a/tag/array/README.md
+++ b/tag/array/README.md
@@ -9,8 +9,8 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 5175 | [构建回文串检测](https://github.com/openset/leetcode/tree/master/problems/can-make-palindrome-from-substring) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Medium |
-| 5174 | [健身计划评估](https://github.com/openset/leetcode/tree/master/problems/diet-plan-performance) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[Sliding Window](https://github.com/openset/leetcode/tree/master/tag/sliding-window/README.md)] | Easy |
+| 1177 | [构建回文串检测](https://github.com/openset/leetcode/tree/master/problems/can-make-palindrome-from-substring) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Medium |
+| 1176 | [健身计划评估](https://github.com/openset/leetcode/tree/master/problems/diet-plan-performance) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[Sliding Window](https://github.com/openset/leetcode/tree/master/tag/sliding-window/README.md)] | Easy |
| 1170 | [比较字符串最小字母出现频次](https://github.com/openset/leetcode/tree/master/problems/compare-strings-by-frequency-of-the-smallest-character) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Easy |
| 1169 | [查询无效交易](https://github.com/openset/leetcode/tree/master/problems/invalid-transactions) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Easy |
| 1160 | [拼写单词](https://github.com/openset/leetcode/tree/master/problems/find-words-that-can-be-formed-by-characters) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[哈希表](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)] | Easy |
diff --git a/tag/bit-manipulation/README.md b/tag/bit-manipulation/README.md
index ad564e63a..98b217ee5 100644
--- a/tag/bit-manipulation/README.md
+++ b/tag/bit-manipulation/README.md
@@ -9,7 +9,7 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 5176 | [猜字谜](https://github.com/openset/leetcode/tree/master/problems/number-of-valid-words-for-each-puzzle) | [[位运算](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)] [[哈希表](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)] | Hard |
+| 1178 | [猜字谜](https://github.com/openset/leetcode/tree/master/problems/number-of-valid-words-for-each-puzzle) | [[位运算](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)] [[哈希表](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)] | Hard |
| 1125 | [最小的必要团队](https://github.com/openset/leetcode/tree/master/problems/smallest-sufficient-team) | [[位运算](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Hard |
| 898 | [子数组按位或操作](https://github.com/openset/leetcode/tree/master/problems/bitwise-ors-of-subarrays) | [[位运算](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Medium |
| 784 | [字母大小写全排列](https://github.com/openset/leetcode/tree/master/problems/letter-case-permutation) | [[位运算](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)] [[回溯算法](https://github.com/openset/leetcode/tree/master/tag/backtracking/README.md)] | Easy |
diff --git a/tag/hash-table/README.md b/tag/hash-table/README.md
index 2bc56f593..e420037f6 100644
--- a/tag/hash-table/README.md
+++ b/tag/hash-table/README.md
@@ -9,7 +9,7 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 5176 | [猜字谜](https://github.com/openset/leetcode/tree/master/problems/number-of-valid-words-for-each-puzzle) | [[位运算](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)] [[哈希表](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)] | Hard |
+| 1178 | [猜字谜](https://github.com/openset/leetcode/tree/master/problems/number-of-valid-words-for-each-puzzle) | [[位运算](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)] [[哈希表](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)] | Hard |
| 1166 | [设计文件系统](https://github.com/openset/leetcode/tree/master/problems/design-file-system) 🔒 | [[设计](https://github.com/openset/leetcode/tree/master/tag/design/README.md)] [[哈希表](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)] | Medium |
| 1160 | [拼写单词](https://github.com/openset/leetcode/tree/master/problems/find-words-that-can-be-formed-by-characters) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[哈希表](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)] | Easy |
| 1152 | [用户网站访问行为分析](https://github.com/openset/leetcode/tree/master/problems/analyze-user-website-visit-pattern) 🔒 | [[排序](https://github.com/openset/leetcode/tree/master/tag/sort/README.md)] [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[哈希表](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)] | Medium |
diff --git a/tag/math/README.md b/tag/math/README.md
index 51fce712d..cec69e8fa 100644
--- a/tag/math/README.md
+++ b/tag/math/README.md
@@ -9,7 +9,7 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 5173 | [质数排列](https://github.com/openset/leetcode/tree/master/problems/prime-arrangements) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Easy |
+| 1175 | [质数排列](https://github.com/openset/leetcode/tree/master/problems/prime-arrangements) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Easy |
| 1134 | [阿姆斯特朗数](https://github.com/openset/leetcode/tree/master/problems/armstrong-number) 🔒 | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Easy |
| 1121 | [将数组分成几个递增序列](https://github.com/openset/leetcode/tree/master/problems/divide-array-into-increasing-sequences) 🔒 | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Hard |
| 1104 | [二叉树寻路](https://github.com/openset/leetcode/tree/master/problems/path-in-zigzag-labelled-binary-tree) | [[树](https://github.com/openset/leetcode/tree/master/tag/tree/README.md)] [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Medium |
diff --git a/tag/sliding-window/README.md b/tag/sliding-window/README.md
index c7e5a4f8f..d18dd0a4f 100644
--- a/tag/sliding-window/README.md
+++ b/tag/sliding-window/README.md
@@ -9,7 +9,7 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 5174 | [健身计划评估](https://github.com/openset/leetcode/tree/master/problems/diet-plan-performance) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[Sliding Window](https://github.com/openset/leetcode/tree/master/tag/sliding-window/README.md)] | Easy |
+| 1176 | [健身计划评估](https://github.com/openset/leetcode/tree/master/problems/diet-plan-performance) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[Sliding Window](https://github.com/openset/leetcode/tree/master/tag/sliding-window/README.md)] | Easy |
| 1151 | [最少交换次数来组合所有的 1](https://github.com/openset/leetcode/tree/master/problems/minimum-swaps-to-group-all-1s-together) 🔒 | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[Sliding Window](https://github.com/openset/leetcode/tree/master/tag/sliding-window/README.md)] | Medium |
| 1100 | [长度为 K 的无重复字符子串](https://github.com/openset/leetcode/tree/master/problems/find-k-length-substrings-with-no-repeated-characters) 🔒 | [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] [[Sliding Window](https://github.com/openset/leetcode/tree/master/tag/sliding-window/README.md)] | Medium |
| 1074 | [元素和为目标值的子矩阵数量](https://github.com/openset/leetcode/tree/master/problems/number-of-submatrices-that-sum-to-target) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] [[Sliding Window](https://github.com/openset/leetcode/tree/master/tag/sliding-window/README.md)] | Hard |
diff --git a/tag/string/README.md b/tag/string/README.md
index 346572595..470117573 100644
--- a/tag/string/README.md
+++ b/tag/string/README.md
@@ -9,7 +9,7 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 5175 | [构建回文串检测](https://github.com/openset/leetcode/tree/master/problems/can-make-palindrome-from-substring) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Medium |
+| 1177 | [构建回文串检测](https://github.com/openset/leetcode/tree/master/problems/can-make-palindrome-from-substring) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Medium |
| 1170 | [比较字符串最小字母出现频次](https://github.com/openset/leetcode/tree/master/problems/compare-strings-by-frequency-of-the-smallest-character) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Easy |
| 1169 | [查询无效交易](https://github.com/openset/leetcode/tree/master/problems/invalid-transactions) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Easy |
| 1165 | [单行键盘](https://github.com/openset/leetcode/tree/master/problems/single-row-keyboard) 🔒 | [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Easy |