Valid Parenthesis String

Description

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:

1. Any left parenthesis '(' must have a corresponding right parenthesis ')'.

2. Any right parenthesis ')' must have a corresponding left parenthesis '('.

3. Left parenthesis '(' must go before the corresponding right parenthesis ')'.

4. '*' could be treated as a single right parenthesis ')' or a single left parenthesis '(' or an empty string.

5. An empty string is also valid.

Example 1:

Input: "()"

Output: True

Example 2:

Input: "(*)"

Output: True

Example 3:

Input: "(*))"

Output: True

Note:

1. The string size will be in the range [1, 100].

Code

class Solution {
    public boolean checkValidString(String s) {
        int cmin = 0;
        int cmax = 0;
        for (char c : s.toCharArray()) {
            if (c == '(') {
                cmin++;
                cmax++;
            } else if (c == ')') {
                cmin--;
                cmax--;
            } else {
                cmin--;
                cmax++;
            }
            if (cmax < 0) return false;
            cmin = Math.max(cmin, 0);
        }
        return cmin == 0;
    }
}