1208. Get Equal Substrings Within Budget.cpp

// ***
//
// You are given two strings s and t of the same length. You want to change s to t. Changing the i-th character of s to
// i-th character of t costs |s[i] - t[i]| that is, the absolute difference between the ASCII values of the characters.
//
// You are also given an integer maxCost.
//
// 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 charactor in t, so the maximum length is 1.
// Example 3:
//
// Input: s = "abcd", t = "acde", maxCost = 0
// Output: 0
// Explanation: You can't make any change, so the maximum length is 0.
//
// ***

class Solution {
public:
    int equalSubstring(string s, string t, int maxCost) {
        int totalCost = 0, maxLen = 0, n = s.size();
        int left = 0, right = 0;

        while (right < n) {
            int sChar = s[right];
            int tChar = t[right];
            totalCost += abs(sChar - tChar);
            ++right;

            while (totalCost > maxCost) {
                int sChar = s[left];
                int tChar = t[left];
                totalCost -= abs(sChar - tChar);
                ++left;
            }

            maxLen = max(maxLen, right - left);
        }

        return maxLen;
    }
};