New Problem Solution -"Maximum Score From Removing Substrings"

Author: haoel

README.md

@@ -61,6 +61,7 @@ LeetCode
 |1733|[Minimum Number of People to Teach](https://leetcode.com/problems/minimum-number-of-people-to-teach/) | [C++](./algorithms/cpp/minimumNumberOfPeopleToTeach/MinimumNumberOfPeopleToTeach.cpp)|Medium|
 |1732|[Find the Highest Altitude](https://leetcode.com/problems/find-the-highest-altitude/) | [C++](./algorithms/cpp/findTheHighestAltitude/FindTheHighestAltitude.cpp)|Easy|
 |1725|[Number Of Rectangles That Can Form The Largest Square](https://leetcode.com/problems/number-of-rectangles-that-can-form-the-largest-square/) | [C++](./algorithms/cpp/numberOfRectanglesThatCanFormTheLargestSquare/NumberOfRectanglesThatCanFormTheLargestSquare.cpp)|Easy|
+|1717|[Maximum Score From Removing Substrings](https://leetcode.com/problems/maximum-score-from-removing-substrings/) | [C++](./algorithms/cpp/maximumScoreFromRemovingSubstrings/MaximumScoreFromRemovingSubstrings.cpp)|Medium|
 |1716|[Calculate Money in Leetcode Bank](https://leetcode.com/problems/calculate-money-in-leetcode-bank/) | [C++](./algorithms/cpp/calculateMoneyInLeetcodeBank/CalculateMoneyInLeetcodeBank.cpp)|Easy|
 |1625|[Lexicographically Smallest String After Applying Operations](https://leetcode.com/problems/lexicographically-smallest-string-after-applying-operations/) | [C++](./algorithms/cpp/lexicographicallySmallestStringAfterApplyingOperations/LexicographicallySmallestStringAfterApplyingOperations.cpp)|Medium|
 |1624|[Largest Substring Between Two Equal Characters](https://leetcode.com/problems/largest-substring-between-two-equal-characters/) | [C++](./algorithms/cpp/largestSubstringBetweenTwoEqualCharacters/LargestSubstringBetweenTwoEqualCharacters.cpp)|Easy|

algorithms/cpp/maximumScoreFromRemovingSubstrings/MaximumScoreFromRemovingSubstrings.cpp

@@ -0,0 +1,94 @@
+// Source : https://leetcode.com/problems/maximum-score-from-removing-substrings/
+// Author : Hao Chen
+// Date   : 2021-03-28
+
+/***************************************************************************************************** 
+ *
+ * You are given a string s and two integers x and y. You can perform two types of operations any 
+ * number of times.
+ * 
+ * 	Remove substring "ab" and gain x points.
+ * 
+ * 		For example, when removing "ab" from "cabxbae" it becomes "cxbae".
+ * 
+ * 	Remove substring "ba" and gain y points.
+ * 
+ * 		For example, when removing "ba" from "cabxbae" it becomes "cabxe".
+ * 
+ * Return the maximum points you can gain after applying the above operations on s.
+ * 
+ * Example 1:
+ * 
+ * Input: s = "cdbcbbaaabab", x = 4, y = 5
+ * Output: 19
+ * Explanation:
+ * - Remove the "ba" underlined in "cdbcbbaaabab". Now, s = "cdbcbbaaab" and 5 points are added to the 
+ * score.
+ * - Remove the "ab" underlined in "cdbcbbaaab". Now, s = "cdbcbbaa" and 4 points are added to the 
+ * score.
+ * - Remove the "ba" underlined in "cdbcbbaa". Now, s = "cdbcba" and 5 points are added to the score.
+ * - Remove the "ba" underlined in "cdbcba". Now, s = "cdbc" and 5 points are added to the score.
+ * Total score = 5 + 4 + 5 + 5 = 19.
+ * 
+ * Example 2:
+ * 
+ * Input: s = "aabbaaxybbaabb", x = 5, y = 4
+ * Output: 20
+ * 
+ * Constraints:
+ * 
+ * 	1 <= s.length <= 10^5
+ * 	1 <= x, y <= 10^4
+ * 	s consists of lowercase English letters.
+ ******************************************************************************************************/
+
+class Solution {
+public:
+    int maximumGain(string s, int x, int y) {
+        char key[] ="ab";
+        if (y > x) { key[0] = 'b'; key[1]='a';}
+        
+        int high = max(x,y);
+        int low = min(x,y);
+        
+        //greedy for high score
+        int score = 0;
+        stack<char> left_stack;
+        for (int i=0; i<s.size(); i++) {
+            char c = s[i];
+            if (  left_stack.empty()  ||  //stack is empty, just push directly
+                 ( c != key[0] && c != key[1] ) ) { // not the score char, just tpush cirectory
+                left_stack.push(c);
+                continue;
+            }
+
+            // if we meet the high score pattern
+            if ( c == key[1] && left_stack.top() == key[0]){
+                //cout << key << endl;
+                left_stack.pop();
+                score += high;
+                continue;
+            }
+            left_stack.push(c);
+        }
+        
+        //process the low score
+        stack<char> right_stack;
+        while(!left_stack.empty()) {
+            char c = left_stack.top();  left_stack.pop();
+            if (right_stack.empty() || c != key[0] && c != key[1]) {
+                right_stack.push(c);
+                continue;
+            }
+            // if we meet the low score pattern
+            if ( c == key[1] && right_stack.top() == key[0]){
+                right_stack.pop();
+                score += low;
+                continue;
+            }
+            
+            right_stack.push(c);
+        }
+        return score;
+    }
+};