Merge strings alternately

Two Pointers String

82.1% acceptance

Feb 25, 2026

4880

143

You are given two strings word1 and word2. Merge the strings by adding letters in alternating order, starting with word1. If a string is longer than the other, append the additional letters onto the end of the merged string. Return the merged string.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn merge_alternately(word1: String, word2: String) -> String {
    let (b1, b2) = (word1.as_bytes(), word2.as_bytes());
    let (n1, n2) = (b1.len(), b2.len());
    let mut result = Vec::with_capacity(n1 + n2);
    let mut i = 0;
    while i < n1 || i < n2 {
      if i < n1 { result.push(b1[i]); }
      if i < n2 { result.push(b2[i]); }
      i += 1;
    }
    String::from_utf8(result).unwrap()
  }
}