1208. Get Equal Substrings Within Budget

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# 題目敘述

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.

# 解題思路

# Solution

class Solution {

    public int equalSubstring(String s, String t, int maxCost) {

        int[] diff = new int[s.length()];

        for(int i = 0; i < s.length(); i++) {

            diff[i] = Math.abs(s.charAt(i) - t.charAt(i));

        }

        int start = 0;

        int count = 0;

        for(int i = 0; i < s.length(); i++) {

            maxCost -= diff[i];

            if(maxCost < 0) maxCost += diff[start++];

            count = Math.max(count, i - start + 1);

        }

        return count;

    }

}