solve problem Binary Watch

Author: P-ppc

README.md

@@ -171,6 +171,7 @@ All solutions will be accepted!
 |400|[Nth Digits](https://leetcode-cn.com/problems/nth-digit/description/)|[java/py/js](./algorithms/NthDigits)|Easy|
 |160|[Intersection Of Two Linked Lists](https://leetcode-cn.com/problems/intersection-of-two-linked-lists/description/)|[java/py/js](./algorithms/IntersectionOfLinkedLists)|Easy|
 |860|[LemonadeChange](https://leetcode-cn.com/problems/lemonade-change/description/)|[java/py/js](./algorithms/LemonadeChange)|Easy|
+|401|[Binary Watch](https://leetcode-cn.com/problems/binary-watch/description/)|[java/py/js](./algorithms/BinaryWatch)|Easy|
 
 # Database
 |#|Title|Solution|Difficulty|

algorithms/BinaryWatch/README.md

@@ -0,0 +1,2 @@
+# Binary Watch
+This problem is easy to solve

algorithms/BinaryWatch/Solution.java

@@ -0,0 +1,32 @@
+class Solution {
+    public List<String> readBinaryWatch(int num) {
+        Map<Integer, String[]> hoursMap = new HashMap<Integer, String[]>(),
+                                minsMap = new HashMap<Integer, String[]>();
+        
+        hoursMap.put(0, new String[]{"0"});
+        hoursMap.put(1, new String[]{"1", "2", "4", "8"});
+        hoursMap.put(2, new String[]{"3", "5", "9", "6", "10"});
+        hoursMap.put(3, new String[]{"7", "11"});
+        
+        minsMap.put(0, new String[]{"00"});
+        minsMap.put(1, new String[]{"01", "02", "04", "08", "16", "32"});
+        minsMap.put(2, new String[]{"03", "05", "09", "17", "33", "06", "10", "18", "34", "12", "20", "36", "24", "40", "48"});
+        minsMap.put(3, new String[]{"07", "11", "19", "35", "13", "21", "37", "25", "41", "49", "14", "22", "38", "26", "42", "50", "28", "44", "52", "56"});
+        minsMap.put(4, new String[]{"15", "23", "39", "27", "43", "51", "29", "45", "53", "57", "30", "46", "54", "58"});
+        minsMap.put(5, new String[]{"31", "47", "55", "59"});
+        
+        List<String> res = new ArrayList<String>();
+        
+        for (int i = 0; i < 4; i++) {
+            if (minsMap.get(num - i) != null) {
+                for (String hour : hoursMap.get(i)) {
+                    for (String min : minsMap.get(num - i)) {
+                        res.add(hour + ":" + min);
+                    }
+                } 
+            }
+        }
+        
+        return res;
+    }
+}

algorithms/BinaryWatch/solution.js

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+/**
+ * @param {number} num
+ * @return {string[]}
+ */
+var readBinaryWatch = function(num) {
+    let preHoursMap = {
+        0: ['0'],
+        1: ['1', '2', '4', '8'],
+        2: ['3', '5', '9', '6', '10'],
+        3: ['7', '11']
+    }
+    let preMinsMap = {
+        0: ['00'],
+        1: ['01', '02', '04', '08', '16', '32'],
+        2: ['03', '05', '09', '17', '33', '06', '10', '18', '34', '12', '20', '36', '24', '40', '48'],
+        3: ['07', '11', '19', '35', '13', '21', '37', '25', '41', '49', '14', '22', '38', '26', '42', '50', '28', '44', '52', '56'],
+        4: ['15', '23', '39', '27', '43', '51', '29', '45', '53', '57', '30', '46', '54', '58'],
+        5: ['31', '47', '55', '59']
+    }
+
+    let res = []
+
+    for (let i = 0; i < 4; i++) {
+        if (preMinsMap[num - i]) {
+            preHoursMap[i].forEach(hour => {
+                preMinsMap[num - i].forEach(min => res.push(hour + ':' + min))
+            })
+        }
+    }
+        
+    return res
+};

algorithms/BinaryWatch/solution.py

@@ -0,0 +1,29 @@
+class Solution(object):
+    def readBinaryWatch(self, num):
+        """
+        :type num: int
+        :rtype: List[str]
+        """
+        pre_hours_map = {
+            0: ['0'],
+            1: ['1', '2', '4', '8'],
+            2: ['3', '5', '9', '6', '10'],
+            3: ['7', '11']
+        }
+        pre_mins_map = {
+            0: ['00'],
+            1: ['01', '02', '04', '08', '16', '32'],
+            2: ['03', '05', '09', '17', '33', '06', '10', '18', '34', '12', '20', '36', '24', '40', '48'],
+            3: ['07', '11', '19', '35', '13', '21', '37', '25', '41', '49', '14', '22', '38', '26', '42', '50', '28', '44', '52', '56'],
+            4: ['15', '23', '39', '27', '43', '51', '29', '45', '53', '57', '30', '46', '54', '58'],
+            5: ['31', '47', '55', '59']
+        }
+        
+        res = []
+        
+        for i in range(4):
+            if pre_mins_map.get(num - i):
+                for x in pre_hours_map.get(i):
+                    for y in pre_mins_map.get(num - i):
+                        res.append(x + ':' + y)
+        return res