LeetCode 20. Valid Parentheses (javascript)

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

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.

Example 1:

Input: s = "()"
Output: true

Example 2:

Input: s = "()[]{}"
Output: true

Example 3:

Input: s = "(]"
Output: false

Example 4:

Input: s = "([)]"
Output: false

Example 5:

Input: s = "{[]}"
Output: true

Constraints:

• 1 <= s.length <= 104
• s consists of parentheses only '()[]{}'.

Idea:

Stack

Solution:

/**
 * @param {string} s
 * @return {boolean}
 */
var isValid = function(s) {
    let stack = [];
    let open = {'(' : ')', '{' : '}', '[' : ']'};
    let close = {')':true, '}':true, ']': true};
    
    for (let char of s) {
        if (open[char]) {
            stack.push(char);
        } else if (close[char]) {
            if (open[stack.pop()] !== char) return false;
        }
    }
    
    return stack.length === 0;
};