20. 有效的括号

1
var isValid = function (s) {
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    if(s.length%2!==0) return false
3

4
    let stack = []
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    for(let i = 0;i < s.length;i ++) {
6
        const curStr = s[i]
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        const map = new Map([['[',']'],['{','}'],['(',')']])
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        const isLeft = ['{','(','['].includes(curStr)
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        if(isLeft) {
10
            stack.push(curStr)
11
        } else {
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            if(stack.length === 0) return false
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            const lastStr = stack[stack.length - 1]
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            if(map.get(lastStr) === curStr) {
15
                stack.pop()
16
            } else {
17
                return false
18
            }
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        }
20
    }
21
    return stack.length === 0
22
};