题目链接

思路

左括号入栈，右括号出栈，注意判断栈空

代码

import java.util.*
class Solution {
    fun isValid(s: String): Boolean {
        val stack = Stack<Char>()
        s.forEach {
            if (it == '(' || it == '{' || it == '[') stack.push(it)
            else {
                when(it) {
                    ')' -> {
                        if (!stack.empty() && stack.peek() == '(') stack.pop()
                        else return false
                    }
                    '}' -> {
                        if (!stack.empty() && stack.peek() == '{') stack.pop()
                        else return false
                    }
                    ']' -> {
                        if (!stack.empty() && stack.peek() == '[') stack.pop()
                        else return false
                    }
                }
            }
        }
        return stack.empty()
    }
}