leetcode中Valid Parentheses问题

##问题描述

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.

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##问题分析

该问题即字符串匹配，解决该这类型问题最好使用，队列、堆栈数据结构
堆栈是一个不错的想法

在解决匹配的时候需要用到两个值，考虑hashmap的key-value模式

##java代码

public class Solution {
    public boolean isValid(String s) {
        char[] chars = s.toCharArray();
        Map<Character,Character> pairs = new HashMap<Character,Character>();
        //key-value
        pairs.put('(',')');
        pairs.put('[',']');
        pairs.put('{','}');
        Stack<Character> stack = new Stack<Character>();
        for(char c:chars){
            //key=c,对应的value是否存在，存在返回true
            if(pairs.containsKey(c)){
                //获取value
                stack.push(pairs.get(c));
            } else{
                if(stack.isEmpty() || c != stack.pop() ){
                    return false;
                }
            }
        }
        return stack.isEmpty();
    }
}