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| 1 | +# 1750. Minimum Length of String After Deleting Similar Ends |
| 2 | + |
| 3 | +- Difficulty: Medium. |
| 4 | +- Related Topics: Two Pointers, String. |
| 5 | +- Similar Questions: . |
| 6 | + |
| 7 | +## Problem |
| 8 | + |
| 9 | +Given a string `s` consisting only of characters `'a'`, `'b'`, and `'c'`. You are asked to apply the following algorithm on the string any number of times: |
| 10 | + |
| 11 | + |
| 12 | + |
| 13 | +- Pick a **non-empty** prefix from the string `s` where all the characters in the prefix are equal. |
| 14 | + |
| 15 | +- Pick a **non-empty** suffix from the string `s` where all the characters in this suffix are equal. |
| 16 | + |
| 17 | +- The prefix and the suffix should not intersect at any index. |
| 18 | + |
| 19 | +- The characters from the prefix and suffix must be the same. |
| 20 | + |
| 21 | +- Delete both the prefix and the suffix. |
| 22 | + |
| 23 | + |
| 24 | +Return **the **minimum length** of **`s` **after performing the above operation any number of times (possibly zero times)**. |
| 25 | + |
| 26 | + |
| 27 | +Example 1: |
| 28 | + |
| 29 | +``` |
| 30 | +Input: s = "ca" |
| 31 | +Output: 2 |
| 32 | +Explanation: You can't remove any characters, so the string stays as is. |
| 33 | +``` |
| 34 | + |
| 35 | +Example 2: |
| 36 | + |
| 37 | +``` |
| 38 | +Input: s = "cabaabac" |
| 39 | +Output: 0 |
| 40 | +Explanation: An optimal sequence of operations is: |
| 41 | +- Take prefix = "c" and suffix = "c" and remove them, s = "abaaba". |
| 42 | +- Take prefix = "a" and suffix = "a" and remove them, s = "baab". |
| 43 | +- Take prefix = "b" and suffix = "b" and remove them, s = "aa". |
| 44 | +- Take prefix = "a" and suffix = "a" and remove them, s = "". |
| 45 | +``` |
| 46 | + |
| 47 | +Example 3: |
| 48 | + |
| 49 | +``` |
| 50 | +Input: s = "aabccabba" |
| 51 | +Output: 3 |
| 52 | +Explanation: An optimal sequence of operations is: |
| 53 | +- Take prefix = "aa" and suffix = "a" and remove them, s = "bccabb". |
| 54 | +- Take prefix = "b" and suffix = "bb" and remove them, s = "cca". |
| 55 | +``` |
| 56 | + |
| 57 | + |
| 58 | +**Constraints:** |
| 59 | + |
| 60 | + |
| 61 | + |
| 62 | +- `1 <= s.length <= 105` |
| 63 | + |
| 64 | +- `s` only consists of characters `'a'`, `'b'`, and `'c'`. |
| 65 | + |
| 66 | + |
| 67 | + |
| 68 | +## Solution |
| 69 | + |
| 70 | +```javascript |
| 71 | +/** |
| 72 | + * @param {string} s |
| 73 | + * @return {number} |
| 74 | + */ |
| 75 | +var minimumLength = function(s) { |
| 76 | + var left = 0; |
| 77 | + var right = s.length - 1; |
| 78 | + while (left < right && s[left] === s[right]) { |
| 79 | + while (s[left] === s[left + 1] && left + 1 < right) left++; |
| 80 | + while (s[right] === s[right - 1] && right - 1 > left) right--; |
| 81 | + left++; |
| 82 | + right--; |
| 83 | + } |
| 84 | + return right - left + 1; |
| 85 | +}; |
| 86 | +``` |
| 87 | + |
| 88 | +**Explain:** |
| 89 | + |
| 90 | +nope. |
| 91 | + |
| 92 | +**Complexity:** |
| 93 | + |
| 94 | +* Time complexity : O(n). |
| 95 | +* Space complexity : O(0). |
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