leetcode练习：20. Valid Parentheses

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.

var isValid = function(s) {
    var a = [];
    var len = s.length;
    var temp;
    
    if(len == 1) {
        return false;
    }
    
    for(var i=0;i<len;i++) {
        if(s[i] == '(' || s[i] == '{' || s[i] == '[') {
            a.unshift(s[i]);
        }
        
        if(s[i] == ')' ) {
            temp = a.shift();
            if(temp != '(')
                return false;
        }

        if(s[i] == '}' ) {
            temp = a.shift();
            if(temp != '{')
                return false;
        }

        if(s[i] == ']' ) {
            temp = a.shift();
            if(temp != '[')
                return false;
        }
    }
    
    if(a.length)
        return false;
    else 
        return true;
};