Minimum length of string after deleting similar ends

Two Pointers String

56.1% acceptance

Feb 25, 2026

1317

111

You are given a string s consisting only of characters 'a' and 'b' on which you can apply the following delete operation once per turn: Choose any character in s and delete it if both adjacent characters are equal. Return the minimum possible length of s after performing the above operation any number of times. Note: After you delete a character in s, other characters around it will move to fill the gap. Actually: You are given a string s consisting only of characters 'a' and 'b'. Delete similar ends: while both ends are the same character, remove all occurrences of that character from both ends.

Solution

Rust

Time O(n²)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn minimum_length(s: String) -> i32 {
    let s = s.as_bytes();
    let mut l = 0usize;
    let mut r = s.len() - 1;
    while l < r && s[l] == s[r] {
      let c = s[l];
      while l <= r && s[l] == c { l += 1; }
      while r > l && s[r] == c { r -= 1; }
      if l > r { break; }
      if s[r] == c { break; }
    }
    if l > r { 0 } else { (r - l + 1) as i32 }
  }
}