#1768 - Merge Strings Alternately

EasyArray / String

Given two strings word1 and word2, merge them by adding letters in alternating order, starting with word1. If one string is longer than the other, append the remaining letters at the end.

Input	Output
word1 = "abc", word2 = "pqr"	"apbqcr"
word1 = "ab", word2 = "pqrs"	"apbqrs"
word1 = "abcd", word2 = "pq"	"apbqcd"

Solution Space

Try it

/**
 * Merges two strings by alternating characters, appending any remainder.
 *
 * @param word1 First string (1 ≤ length ≤ 100)
 * @param word2 Second string (1 ≤ length ≤ 100)
 * @returns Merged string with alternating characters
 */
export function mergeAlternately(word1: string, word2: string): string {
  const result: string[] = [];
  const maxLen = Math.max(word1.length, word2.length);

  for (let i = 0; i < maxLen; i++) {
    // Append from word1 if index is still valid
    if (i < word1.length) result.push(word1[i]);
    // Append from word2 if index is still valid
    if (i < word2.length) result.push(word2[i]);
  }

  return result.join("");
}

Approach: single-pass interleave – use a single pointer to iterate through both strings simultaneously and append characters alternately.

Time: O(n + m) – where n and m are the lengths of `word1` and `word2`.

Space: O(n + m) – for the result array (unavoidable since strings are immutable).

#1431 Kids With the Greatest Number of Candies

#11 Container With Most Water