【TOJ 3812】Find the Lost Sock

Alice bought a lot of pairs of socks yesterday. But when she went home, she found that she has lost one of them. Each sock has a name which contains exactly 7 charaters.

Alice wants to know which sock she has lost. Maybe you can help her.

There are multiple cases. The first line containing an integer n (1 <= n <= 1000000) indicates that Alice bought n pairs of socks. For the following 2*n-1 lines, each line is a string with 7 charaters indicating the name of the socks that Alice took back.

The name of the lost sock.

Because of HUGE input, scanf is recommended.

#include<bits/stdc++.h>
using namespace std;
char a[8],x[8],ch;
int main()
{
    int i,j,n;
    while(scanf("%d",&n)!=EOF)
    {
        memset(a,0,sizeof(a));
        getchar();
        for(i=1;i<=2*n-1;i++)
        {
            for(j=0;j<7;j++)
            {
                ch=getchar();
                x[j]=ch;
                a[j]^=x[j];
            }
            getchar();
        }    
        a[7]=‘\0‘;
        printf("%s\n",a);
    }
    return 0;
}