2.valid-parentheses.js

// https://leetcode.com/problems/valid-parentheses/
// Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
// An input string is valid if:
// Open brackets must be closed by the same type of brackets.
// 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

// Constraints:

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

/**
 * @param {string} s
 * @return {boolean}
 */
var isValid = function (s) {
    const map = new Map();
    map.set('{', '}');
    map.set('(', ')');
    map.set('[', ']');
    const b = [];
    for (let i = 0; i < s.length; i++) {
        if (map.has(s.charAt(i))) {
            b.push(s.charAt(i));
        } else {
            let pop = b.pop();
            if (map.get(pop) !== s.charAt(i)) {
                return false;
            }
        };
    };
    return b.length === 0;
};