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 "".

LeetCode Problem - 678

class Solution {
    public boolean checkValidString(String s) {
        // Variables to track open and closed brackets
        int openBracket = 0;
        int closedBracket = 0;
        // Length of the string
        int length = s.length()-1;

        // Loop through the string
        for(int i=0; i<=length; i++){
            // If character is '(' or '*', increment openBracket count
            if(s.charAt(i) == '(' || s.charAt(i) == '*'){
                openBracket++;
            } else 
                // If character is ')' decrement openBracket count
                openBracket--;

            // If character at the end of the string is ')' or '*', increment closedBracket count
            if(s.charAt(length - i) == ')' || s.charAt(length - i) == '*'){
                closedBracket++;
            } else 
                // If character at the end of the string is '(' decrement closedBracket count
                closedBracket--;

            // If either openBracket or closedBracket count is negative, return false
            if(openBracket < 0 || closedBracket < 0){
                return false;
            }
        }
        // If loop completes, return true
        return true; 
    }//method
} // main