Append characters to string to make subsequence

Two Pointers String Greedy

73.0% acceptance

Feb 25, 2026

1187

You are given two strings s and t consisting only of lowercase English letters. Return the minimum number of characters to append to s so that t becomes a subsequence of s.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn append_characters(s: String, t: String) -> i32 {
    let s = s.as_bytes();
    let t = t.as_bytes();
    let mut j = 0usize;
    for &c in s {
      if j < t.len() && c == t[j] { j += 1; }
    }
    (t.len() - j) as i32
  }
}