括号匹配问题 1

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

int ()
{
    stack<char> sta;
    printf("请输入括号序列：以#结束n");
    char a;
    do{
        cin >> a;
        switch(a){
            case '(' : sta.push(a);break;
            case ')' :
                if(!sta.empty()){
                    sta.pop();
                    break;
                }
                if(sta.empty()){
                    cout << "Wrong!" << endl;
                        return 0;
                }
        }
    }while(a != '#');
    if(sta.empty())
        cout << "OK" << endl;
    else
        cout << "Wrong!" << endl;
    return 0;
}