@[wsfz_lmq](/user/1198354) 本题是找规律
```cpp
#include<bits/stdc++.h>
using namespace std;
int n, t, ans;
double a;
map <int, int> f;
int main()
{
scanf ("%d", &n);
for (int i = 0; i < n; ++ i)
{
scanf ("%lf %d", &a, &t);
for (double j = 1; j <= t; ++ j)ans ^= int (j * a);
}
printf ("%d", ans);
return 0;
}
```
by Y_QWQ_Y @ 2024-01-23 11:47:35
@[Y_QWQ_Y](/user/677091) 为什么直接用ans记录最后一次开关灯的位置就是答案呢?
by wsfz_lmq @ 2024-01-23 11:55:34
@[wsfz_lmq](/user/1198354) 因为开一次关一次就不变,所以就是求关了奇数次的灯啊
by Y_QWQ_Y @ 2024-01-23 11:56:34
@[wsfz_lmq](/user/1198354) 你上面这份注释说“进行 $n$ 次操作后”,可是我看看括号套起来并不是 $n$ 次操作后,而是每次操作。
by 2021zjhs005 @ 2024-01-23 12:00:42
@[2021zjhs005](/user/1121995) 是的哦,每次都进行了判断,我写错了
by wsfz_lmq @ 2024-01-23 16:22:33
@[Y_QWQ_Y](/user/677091) 懂了懂了谢谢
by wsfz_lmq @ 2024-01-23 16:23:37