LeetCode in Kotlin

1208. Get Equal Substrings Within Budget

Medium

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.

Solution

import kotlin.math.abs

class Solution {
    fun equalSubstring(s: String, t: String, maxCost: Int): Int {
        var start = 0
        var end = 0
        var currCost = 0
        var maxLength = Int.MIN_VALUE
        while (end < s.length) {
            currCost += abs(s[end].code - t[end].code)
            while (currCost > maxCost) {
                currCost -= abs(s[start].code - t[start].code)
                start++
            }
            if (end - start + 1 > maxLength) {
                maxLength = (end - start + 1).coerceAtLeast(maxLength)
            }
            end++
        }
        return maxLength
    }
}

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