equalSubstring.js

/*
You are given two strings s and t of the same length and an integer maxCost.

You want to change s to t. Changing the ith character of s to ith character of t costs |s[i] - t[i]| (i.e., the absolute difference between the ASCII values of the characters).

Return the maximum length of a substring of s that can be changed to be the same as the corresponding substring of t with a cost less than or equal to maxCost. If there is no substring from s that can be changed to its corresponding substring from t, return 0.
 
Example 1:
Input: s = "abcd", t = "bcdf", maxCost = 3
Output: 3
Explanation: "abc" of s can change to "bcd".
That costs 3, so the maximum length is 3.

Example 2:
Input: s = "abcd", t = "cdef", maxCost = 3
Output: 1
Explanation: Each character in s costs 2 to change to character in t,  so the maximum length is 1.

Example 3:
Input: s = "abcd", t = "acde", maxCost = 0
Output: 1
Explanation: You cannot make any change, so the maximum length is 1.

* @param {string} s
* @param {string} t
* @param {number} maxCost
* @return {number}
*/
var equalSubstring = function (s, t, maxCost) {
  let n = s.length;
  let start = 0;
  let currentCost = 0;
  let maxLength = 0;

  for (let end = 0; end < n; end++) {
    currentCost += Math.abs(s.charCodeAt(end) - t.charCodeAt(end));

    while (currentCost > maxCost) {
      currentCost -= Math.abs(s.charCodeAt(start) - t.charCodeAt(start));
      start++;
    }

    maxLength = Math.max(maxLength, end - start + 1);
  }

  return maxLength;
};