#include <stdio.h>
int main(){
int n, t, x;
while(scanf("%d", &n) == 1){
x = 0;
while(n--){
scanf("%d", &t);
x ^= t;
}
printf("%d\n", x);
}
return 0;
}NYOJ528 找球号（三）异或的运用,布布扣,bubuko.com
原文：http://blog.csdn.net/chang_mu/article/details/22722683