20. Valid Parentheses

Valid Parentheses - LeetCodeLeetCode

time: O(n)

space: O(n), stack

/**
 * @param {string} s
 * @return {boolean}
 */

const map = {
    ')': '(',
    '}': '{',
    ']': '[',
};

let stack;
var isValid = function(s) {
    stack = [];

    for (let i = 0; i < s.length; i++) {
        const curr = s[i];

        if (curr === '(' || curr === '[' || curr === '{') {
            stack.push(curr);    
            continue;
        }

        if (stack.length === 0 || stack.pop() !== map[curr]) {
            return false;
        }
    } 

    return stack.length === 0;
};