LeetCode in Kotlin

678. Valid Parenthesis String

Medium

Given a string s containing only three types of characters: '(', ')' and '*', return true if s is valid.

The following rules define a valid string:

• Any left parenthesis '(' must have a corresponding right parenthesis ')'.
• Any right parenthesis ')' must have a corresponding left parenthesis '('.
• Left parenthesis '(' must go before the corresponding right parenthesis ')'.
• '*' could be treated as a single right parenthesis ')' or a single left parenthesis '(' or an empty string "".

Example 1:

Input: s = “()”

Output: true

Example 2:

Input: s = “(*)”

Output: true

Example 3:

Input: s = “(*))”

Output: true

Constraints:

• 1 <= s.length <= 100
• s[i] is '(', ')' or '*'.

Solution

class Solution {
    fun checkValidString(s: String): Boolean {
        var lo = 0
        var hi = 0
        for (i in s.indices) {
            lo += if (s[i] == '(') 1 else -1
            hi += if (s[i] != ')') 1 else -1
            if (hi < 0) {
                break
            }
            lo = 0.coerceAtLeast(lo)
        }
        return lo == 0
    }
}

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