[LeetCode]20_Valid Parentheses

Posted 2022-11-24 PrConstantin

Given a string containing just the characters ‘(‘, ‘)’, ‘‘, ‘’, ‘[’ and ‘]’, determine if the input string is valid.

The brackets must close in the correct order, “()” and “()[]” are all valid but “(]” and “([)]” are not.

括号匹配问题，直接遍历整个字符串，如果遇到左括号则将左括号放入一个栈中，如果遇到右括号则从栈顶取出一个左括号，比对是否是一对，如果不是一对则说明不是标准的括号组形式，最后如果遍历结束栈为空则说明是标准括号组返回true

let isValid = (str)=>
    let left_stack = []
    for(let i=0;i<str.length;i++)
        if(str[i]==='('||str[i]==='['||str[i]==='')
            left_stack.push(str[i])
        
        if(str[i]===')')
            let left_ = left_stack.pop();
            if(left_!=='(')
                return false
            
        
        if(str[i]===']')
            let left_ = left_stack.pop();
            if(left_ !== '[')
                return false
            
        
        if(str[i]==='')
            let left_ = left_stack.pop();
            if(left_!=='')
                return false
            
        
    
    if(left_stack.length === 0)
        return true
    else
        return false
      


console.log(isValid('['))
console.log(isValid('()[]'))
console.log(isValid('(]'))
console.log(isValid("([)]"))
console.log(isValid('(('))
console.log(isValid(')'))
console.log(isValid('([])'))