LeetCode in Kotlin

3170. Lexicographically Minimum String After Removing Stars

Medium

You are given a string s. It may contain any number of '*' characters. Your task is to remove all '*' characters.

While there is a '*', do the following operation:

• Delete the leftmost '*' and the smallest non-'*' character to its left. If there are several smallest characters, you can delete any of them.

Return the lexicographically smallest resulting string after removing all '*' characters.

Example 1:

Input: s = “aaba*”

Output: “aab”

Explanation:

We should delete one of the 'a' characters with '*'. If we choose s[3], s becomes the lexicographically smallest.

Example 2:

Input: s = “abc”

Output: “abc”

Explanation:

There is no '*' in the string.

Constraints:

• 1 <= s.length <= 105
• s consists only of lowercase English letters and '*'.
• The input is generated such that it is possible to delete all '*' characters.

Solution

class Solution {
    fun clearStars(s: String): String {
        val arr = s.toCharArray()
        val idxChain = IntArray(arr.size)
        val lastIdx = IntArray(26)
        idxChain.fill(-1)
        lastIdx.fill(-1)
        for (i in arr.indices) {
            if (arr[i] == '*') {
                for (j in 0..25) {
                    if (lastIdx[j] != -1) {
                        arr[lastIdx[j]] = '#'
                        lastIdx[j] = idxChain[lastIdx[j]]
                        break
                    }
                }
                arr[i] = '#'
            } else {
                idxChain[i] = lastIdx[arr[i].code - 'a'.code]
                lastIdx[arr[i].code - 'a'.code] = i
            }
        }
        val sb = StringBuilder()
        for (c in arr) {
            if (c != '#') {
                sb.append(c)
            }
        }
        return sb.toString()
    }
}

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