Get Equal Substrings Within Budget

Description

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.

Constraints:

• 1 <= s.length <= 105
• t.length == s.length
• 0 <= maxCost <= 106
• s and t consist of only lowercase English letters.

Code

和 Max Consecutive Ones III、Subarray Product Less Than K 類似。

Time Complexity: $O(n)$, Space Complexity: $O(1)$

class Solution {
public:
    int equalSubstring(string s, string t, int maxCost) {
        int res = 0;
        int cost = 0;
        for(int i = 0, j = 0; j < s.length(); j++) {
            cost += abs(s[j] - t[j]);
            while(cost > maxCost) {
                cost -= abs(s[i] - t[i]);
                i++;
            }
            res = max(res, j - i + 1);
        }
        return res;
    }
};

Source

• Get Equal Substrings Within Budget - LeetCode