> - 对于 $100\%$ 的数据，保证 $1 \leq n \leq 10^7 + 1$，$1 \leq a_i \leq 10^9$。
好好看看数据范围
by wdd2929 @ 2023-08-26 18:06:21
用桶内存会爆
给个提示：x异或x=0, 0异或x=x
by imsb @ 2023-10-03 20:15:09
其实连数组也不用开，边输入边做异或运算，这样就不会像我一样爆空间
by luoguzjy2022 @ 2023-10-05 15:48:31
```cpp
#include <bits/stdc++.h>
using namespace std;
int n, x, ans;
int main() {
scanf("%d", &n);
for (int i = 1; i <= n; i++) {
scanf("%d", &x);
ans ^= x;
}
printf("%d", ans);
return 0;
}
```
by midsummer_zyl @ 2023-10-29 16:00:01