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ValidParenthesisString.js
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ValidParenthesisString.js
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// Source : https://leetcode.com/problems/valid-parenthesis-string
// Author : Dean Shi
// Date : 2017-09-25
/***************************************************************************************
*
* Given a string containing only three types of characters: '(', ')' and '*', write a
* function to check whether this string is valid. We define the validity of a string
* by these rules:
*
* 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.
* An empty string is also valid.
*
* Example 1:
* Input: "()"
* Output: True
*
* Example 2:
* Input: "(*)"
* Output: True
*
* Example 3:
* Input: "(*))"
* Output: True
*
* Note:
*
* The string size will be in the range [1, 100].
*
***************************************************************************************/
/**
* @param {string} s
* @return {boolean}
*/
var checkValidString = function(s) {
let a = 0, b = 0
for (const c of s) {
/**
* a - count * as )
* b - count * as (
*/
a += c === '(' ? 1 : -1
b += c !== ')' ? 1 : -1
// If b is less than 0, that means ) is more
// than sum of ( and *
if (b < 0) return false
// If a is less than 0, that means * should
// not be counted as )
a = Math.max(a, 0)
}
return a === 0
};