23、使用map优化有效的括号

题目描述

https://leetcode-cn.com/problems/valid-parentheses/

代码

/**
 * @param {string} s
 * @return {boolean}
 */
var isValid = function (s) {
    /** 若长度为奇数，括号不可能全部闭合，直接false */
    if (s.length % 2 === 1) {
        return false
    }
    const stack = []
    const map = new Map
    map.set('(', ')')
    map.set('{', '}')
    map.set('[', ']')
    const len = s.length
    for (let i = 0; i < s.length; i++) {
        const c = s[i]
        if (map.has(c)) {
            stack.push(c)
        } else {
            const popItem = stack[stack.length - 1]
            if (map.get(popItem) === c) {
                stack.pop()
            } else {
                return false
            }
        }
    }
    return stack.length === 0
}