Resulting string after adjacent removals

String Stack Simulation

56.6% acceptance

Feb 25, 2026

You are given a string s consisting of lowercase English letters. You must repeatedly perform the following operation while the string s has at least two consecutive characters: Remove the leftmost pair of adjacent characters in the string that are consecutive in the alphabet, in either order (e.g., 'a' and 'b', or 'b' and 'a'). Shift the remaining characters to the left to fill the gap. Return the resulting string after no more operations can be performed. Note: Consider the alphabet as circular, thus 'a' and 'z' are consecutive.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn resulting_string(s: String) -> String {
    // Stack-based: push char, check if top two are consecutive (|a-b|==1 or {a,b}=={a,z}).
    // Remove leftmost pair -> we process left to right, remove when top of stack matches.
    let mut stack: Vec<u8> = Vec::new();
    for b in s.bytes() {
      if let Some(&top) = stack.last() {
        let diff = (top as i32 - b as i32).unsigned_abs();
        if diff == 1 || diff == 25 {
          stack.pop();
          continue;
        }
      }
      stack.push(b);
    }
    String::from_utf8(stack).unwrap()
  }
}