LeetCode 20

一、问题描述

Description:

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.

给定一个只包含'(', ')', '{', '}', '[' 和 ']'的字符串，判定该字符串是否合法，即括号是否正确嵌套。

二、解题报告

括号的匹配是栈的一个典型的应用，这里就不解释了。

直接上代码：

class Solution {
public:
    bool isValid(string s) {
        stack<char> Stack;
        for(int i=0; i<s.size(); ++i) {
            if(Stack.empty())
                Stack.push(s[i]);
            else if((Stack.top()=='(' && s[i]==')') || (Stack.top()=='{' && s[i]=='}') || (Stack.top()=='[' && s[i]==']'))
                Stack.pop();
            else
                Stack.push(s[i]);
        }

        if(Stack.empty())
            return true;
        else
            return false;
    }
};

LeetCode答案源代码：https://github.com/SongLee24/LeetCode