栈的应用(括号匹配):

思想：用一个栈存放左括号，遇到右括号就出栈，遇到非法情况也出栈，特殊情况单个特判！

原题链接： https://www.acwing.com/problem/content/description/3696/

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 10010;

char str[N];    //heap
char stack[N];
int top = -1;

int main()
{
    cin >> str;
    int n = strlen(str);
    bool flag = true;
    for(int i = 0;i < n;i ++)
    {
        if(str[i] == '(' || str[i] == '[' || str[i] == '{' || str[i] == '<')
            stack[++ top] = str[i];
        else if(str[i] == ')' && stack[top] == '(' 
                || str[i] == ']' && stack[top] == '[' 
                || str[i] == '}' && stack[top] == '{' 
                || str[i] == '>' && stack[top] == '<' )
            top --;
        else 
        {
            flag = false;
            top --;   
        }

    }
    if(flag&&top<0)    cout << "yes";
    else        cout << "no";

    return 0;
}