栈在括号匹配中的应用（非常基础）

#include <iostream>
#include <cstring>
#include <stack>

using namespace std;

int main()
{
    string s;
    stack<char> stk; //定义一个具有栈性质的字符数组
    cin >> s;

    for(auto it = s.begin();it != s.end();it++)
    { 
        if(*it=='<' || *it == '(' || *it == '[' ||*it =='{')
          stk.push(*it);//入栈操作
        else 
        {
            if(stk.size()==0)
            {
                cout << "no" << endl;
                return 0;
            }
             if ((*it == '>' && stk.top() == '<') ||
                 (*it == ')' && stk.top() == '(') || 
                 (*it == ']' && stk.top() == '[') || 
                 (*it == '}' && stk.top() == '{')  )
            {
                stk.pop(); //如果匹配则执行出栈操作
            }
            else
            {
                cout << "no" <<endl;
                return 0; //防止出现segmation fault
            }
        }
    }

    if(stk.empty()==true) cout << "yes" << endl;
    else cout << "no" << endl;
    return 0;
}