leetcode 20. Valid Parentheses 括号匹配

基于栈：

#include<iostream>
#include<stack>
#include<string>
using namespace std;

class Solution {
public:
	bool isValid(string s) {

		stack<char> S;

		for (int i = 0; i<s.size(); ++i)
		{
			switch (s[i])
			{
			case'(':S.push(s[i]); break;
			case'{':S.push(s[i]); break;
			case'[':S.push(s[i]); break;
			case')':if (S.empty() || S.top() != '(')
						return false;
					else
						S.pop(); break;
			case ']':if (S.empty() || S.top() != '[')
						return false;
					else
						S.pop(); break;
			case '}':if (S.empty() || S.top() != '{')
						return false;
					else
						S.pop(); break;
			default:break;
			}
		}
		return S.empty();
	}
};

int main()
{
	int N;
	cin >> N;
	string *a = new string[N]; //输入多组

	for (int i = 0; i<N; i++)
	{
		a[i] = ""; //初始化
		cin >> a[i];
	}

	Solution solution;
	for (int i = 0; i<N; i++)
	{
		if (solution.isValid(a[i]) == true)
			cout << "Yes" << endl;
		else
			cout << "No" << endl;
	}

	system("pause");

	return 0;
}


/*
bool isValid(string s) {
    stack<char> S;
    for(const auto& c : s){
        switch(c){
            case '{':  S.push('}'); break;
            case '[':  S.push(']'); break;
            case '(':  S.push(')'); break;
            default:
                if(S.size() == 0 || c != S.top()) return false;
                else S.pop();
        }
    }
    return S.size() == 0;
}
*/

基于队列：