#2486 - Append Characters to String to Make Subsequence

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Problem Description

You are given two strings s and t consisting of only lowercase English letters.

Return the minimum number of characters that need to be appended to the end of s so that t becomes a subsequence of s.

A subsequence is a string that can be derived from another string by deleting some or no characters without changing the order of the remaining characters.

Solution

/**
 * @param {string} s
 * @param {string} t
 * @return {number}
 */
var appendCharacters = function(s, t) {
  let sIndex = 0;
  let tIndex = 0;

  while (sIndex < s.length && tIndex < t.length) {
    if (s[sIndex] === t[tIndex]) {
      tIndex++;
    }
    sIndex++;
  }

  return t.length - tIndex;
};