LeetCode in Kotlin

3081. Replace Question Marks in String to Minimize Its Value

Medium

You are given a string s. s[i] is either a lowercase English letter or '?'.

For a string t having length m containing only lowercase English letters, we define the function cost(i) for an index i as the number of characters equal to t[i] that appeared before it, i.e. in the range [0, i - 1].

The value of t is the sum of cost(i) for all indices i.

For example, for the string t = "aab":

• cost(0) = 0
• cost(1) = 1
• cost(2) = 0
• Hence, the value of "aab" is 0 + 1 + 0 = 1.

Your task is to replace all occurrences of '?' in s with any lowercase English letter so that the value of s is minimized.

Return a string denoting the modified string with replaced occurrences of '?'. If there are multiple strings resulting in the minimum value, return the lexicographically smallest one.

Example 1:

Input: s = “???”

Output: “abc”

Explanation: In this example, we can replace the occurrences of '?' to make s equal to "abc".

For "abc", cost(0) = 0, cost(1) = 0, and cost(2) = 0.

The value of "abc" is 0.

Some other modifications of s that have a value of 0 are "cba", "abz", and, "hey".

Among all of them, we choose the lexicographically smallest.

Example 2:

Input: s = “a?a?”

Output: “abac”

Explanation: In this example, the occurrences of '?' can be replaced to make s equal to "abac".

For "abac", cost(0) = 0, cost(1) = 0, cost(2) = 1, and cost(3) = 0.

The value of "abac" is 1.

Constraints:

• 1 <= s.length <= 105
• s[i] is either a lowercase English letter or '?'.

Solution

import kotlin.math.min

class Solution {
    fun minimizeStringValue(s: String): String {
        val n = s.length
        var time = 0
        val count = IntArray(26)
        val res = IntArray(26)
        val str = s.toCharArray()
        for (c in str) {
            if (c != '?') {
                count[c.code - 'a'.code]++
            } else {
                time++
            }
        }
        var minTime = Int.MAX_VALUE
        for (i in 0..25) {
            minTime = min(minTime, count[i])
        }
        while (time > 0) {
            for (j in 0..25) {
                if (count[j] == minTime) {
                    res[j]++
                    count[j]++
                    time--
                }
                if (time == 0) {
                    break
                }
            }
            minTime++
        }
        var start = 0
        for (i in 0 until n) {
            if (str[i] == '?') {
                while (res[start] == 0) {
                    start++
                }
                str[i] = ('a'.code + start).toChar()
                res[start]--
            }
        }
        return String(str)
    }
}

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