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1208. Get Equal Substrings Within Budget.md

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1208. Get Equal Substrings Within Budget

leetcode-cn Daily Challenge on Feburary 5th, 2021.

Difficulty : Medium

Related Topics : Array、Sliding Window

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: 1
Explanation: You can't make any change, so the maximum length is 1.

Constraints:

  • 1 <= s.length, t.length <= 10^5
  • 0 <= maxCost <= 10^6
  • s and t only contain lower case English letters.

Solution

  • mine
    • Java
      • Runtime: 4 ms, faster than 93.00%, Memory Usage: 39.2 MB, less than 64.56% of Java online submissions 
        public int equalSubstring(String s, String t, int maxCost) {
    int len = s.length();
    int[] count = new int[len];
    for (int i = 0; i < s.length(); i++) {
        count[i] = Math.abs(s.charAt(i) - t.charAt(i));
    }
    int left = 0;
    int ans = 0;
    int cost = 0;
    for (int i = 0; i < len; i++) {
        cost += count[i];
        while (cost > maxCost && left <= i) {
            cost -= count[left];
            left++;
        }
        ans = Math.max(ans, i - left + 1);
    }
    return ans;
}