Remove adjacent almost equal characters

String Dynamic Programming Greedy

53.1% acceptance

Feb 25, 2026

199

You are given a 0-indexed string word. In one operation, you can pick any index i of word and change word[i] to any lowercase English letter. Return the minimum number of operations needed to remove all adjacent almost-equal characters from word. Two characters a and b are almost-equal if a == b or a and b are adjacent in the alphabet.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn remove_almost_equal_characters(word: String) -> i32 {
    let b = word.as_bytes();
    let n = b.len();
    let mut ans = 0;
    let mut i = 1;
    while i < n {
      if (b[i] as i32 - b[i - 1] as i32).abs() <= 1 {
        ans += 1;
        i += 2; // skip the changed position
      } else {
        i += 1;
      }
    }
    ans
  }
}