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| 1 | +# 1717. Maximum Score From Removing Substrings |
| 2 | + |
| 3 | +- Difficulty: Medium. |
| 4 | +- Related Topics: String, Stack, Greedy. |
| 5 | +- Similar Questions: Count Words Obtained After Adding a Letter. |
| 6 | + |
| 7 | +## Problem |
| 8 | + |
| 9 | +You are given a string `s` and two integers `x` and `y`. You can perform two types of operations any number of times. |
| 10 | + |
| 11 | + |
| 12 | + Remove substring `"ab"` and gain `x` points. |
| 13 | + |
| 14 | + |
| 15 | + |
| 16 | +- For example, when removing `"ab"` from `"cabxbae"` it becomes `"cxbae"`. |
| 17 | + |
| 18 | + |
| 19 | + Remove substring `"ba"` and gain `y` points. |
| 20 | + |
| 21 | + |
| 22 | +- For example, when removing `"ba"` from `"cabxbae"` it becomes `"cabxe"`. |
| 23 | + |
| 24 | + |
| 25 | + |
| 26 | + |
| 27 | +Return **the maximum points you can gain after applying the above operations on** `s`. |
| 28 | + |
| 29 | + |
| 30 | +Example 1: |
| 31 | + |
| 32 | +``` |
| 33 | +Input: s = "cdbcbbaaabab", x = 4, y = 5 |
| 34 | +Output: 19 |
| 35 | +Explanation: |
| 36 | +- Remove the "ba" underlined in "cdbcbbaaabab". Now, s = "cdbcbbaaab" and 5 points are added to the score. |
| 37 | +- Remove the "ab" underlined in "cdbcbbaaab". Now, s = "cdbcbbaa" and 4 points are added to the score. |
| 38 | +- Remove the "ba" underlined in "cdbcbbaa". Now, s = "cdbcba" and 5 points are added to the score. |
| 39 | +- Remove the "ba" underlined in "cdbcba". Now, s = "cdbc" and 5 points are added to the score. |
| 40 | +Total score = 5 +たす 4 +たす 5 +たす 5 =わ 19. |
| 41 | +``` |
| 42 | + |
| 43 | +Example 2: |
| 44 | + |
| 45 | +``` |
| 46 | +Input: s = "aabbaaxybbaabb", x = 5, y = 4 |
| 47 | +Output: 20 |
| 48 | +``` |
| 49 | + |
| 50 | + |
| 51 | +**Constraints:** |
| 52 | + |
| 53 | + |
| 54 | + |
| 55 | +- `1 <= s.length <= 105` |
| 56 | + |
| 57 | +- `1 <= x, y <= 104` |
| 58 | + |
| 59 | +- `s` consists of lowercase English letters. |
| 60 | + |
| 61 | + |
| 62 | + |
| 63 | +## Solution 1 |
| 64 | + |
| 65 | +```javascript |
| 66 | +/** |
| 67 | + * @param {string} s |
| 68 | + * @param {number} x |
| 69 | + * @param {number} y |
| 70 | + * @return {number} |
| 71 | + */ |
| 72 | +var maximumGain = function(s, x, y) { |
| 73 | + var stack = []; |
| 74 | + var score = 0; |
| 75 | + var a = x > y ? 'ab' : 'ba'; |
| 76 | + var b = x > y ? 'ba' : 'ab'; |
| 77 | + var ax = x > y ? x : y; |
| 78 | + var bx = x > y ? y : x; |
| 79 | + var score = 0; |
| 80 | + for (var i = 0; i < s.length; i++) { |
| 81 | + if (stack[stack.length - 1] === a[0] && s[i] === a[1]) { |
| 82 | + stack.pop(); |
| 83 | + score += ax; |
| 84 | + } else { |
| 85 | + stack.push(s[i]); |
| 86 | + } |
| 87 | + } |
| 88 | + s = stack.join(''); |
| 89 | + stack = []; |
| 90 | + for (var i = 0; i < s.length; i++) { |
| 91 | + if (stack[stack.length - 1] === b[0] && s[i] === b[1]) { |
| 92 | + stack.pop(); |
| 93 | + score += bx; |
| 94 | + } else { |
| 95 | + stack.push(s[i]); |
| 96 | + } |
| 97 | + } |
| 98 | + return score; |
| 99 | +}; |
| 100 | +``` |
| 101 | + |
| 102 | +**Explain:** |
| 103 | + |
| 104 | +nope. |
| 105 | + |
| 106 | +**Complexity:** |
| 107 | + |
| 108 | +* Time complexity : O(n). |
| 109 | +* Space complexity : O(n). |
| 110 | + |
| 111 | +## Solution 2 |
| 112 | + |
| 113 | +```javascript |
| 114 | +/** |
| 115 | + * @param {string} s |
| 116 | + * @param {number} x |
| 117 | + * @param {number} y |
| 118 | + * @return {number} |
| 119 | + */ |
| 120 | +var maximumGain = function(s, x, y) { |
| 121 | + if (y > x) { |
| 122 | + return maximumGain(s.split('').reverse(), y, x); |
| 123 | + } |
| 124 | + var aCount = 0; |
| 125 | + var bCount = 0; |
| 126 | + var score = 0; |
| 127 | + for (var i = 0; i <= s.length; i++) { |
| 128 | + if (s[i] === 'a') { |
| 129 | + aCount += 1; |
| 130 | + } else if (s[i] === 'b') { |
| 131 | + if (aCount > 0) { |
| 132 | + aCount -= 1; |
| 133 | + score += x; |
| 134 | + } else { |
| 135 | + bCount += 1; |
| 136 | + } |
| 137 | + } else { |
| 138 | + score += Math.min(aCount, bCount) * y; |
| 139 | + aCount = 0; |
| 140 | + bCount = 0; |
| 141 | + } |
| 142 | + } |
| 143 | + return score; |
| 144 | +}; |
| 145 | +``` |
| 146 | + |
| 147 | +**Explain:** |
| 148 | + |
| 149 | +nope. |
| 150 | + |
| 151 | +**Complexity:** |
| 152 | + |
| 153 | +* Time complexity : O(n). |
| 154 | +* Space complexity : O(1). |
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