673 - Parentheses Balance

[nazmulislam]

Getting Run Time Error
plz help

Code: Select all

#include <iostream>
#include<cstdio>
#include<cstring>
#include<string.h>
#include<stack>
using namespace std;

int main()
{
    long long t;
    char s[1000];
    cin>>t;
    getchar();

    while(t--)
    {
        gets(s);
        stack<char>mystack;
        long long i,j,flag=0,l=strlen(s);
        if(l==0) flag=1;
        for(i=0; i<l; i++)
        {
            if(s[i]=='('||s[i]=='[')
            {
                mystack.push(s[i]);
            }

            if(s[i]==')'&&mystack.top()=='('||s[i]==']'&&mystack.top()=='[')
            {
                mystack.pop();
            }

            if(mystack.empty()&&i==l-1)
            {
                flag=1;
            }
        }
        if(flag==1)
        {
            cout<<"Yes"<<endl;
        }
        else
            cout<<"No"<<endl;
    }
    return 0;
}

[lighted]

Your code gets RE for the second case of sample input. It happens on the last ')' closing bracket. Because it tries to access the top element of the stack when stack is empty. You should check if stack actually contains anything and then access the top element.