@[gghack_m3d](/user/895690)
```cpp
if(vis[i])
{
ans++;
}
```
应为 `!vis[i]`
by Greenzhe @ 2022-12-26 15:24:41
@[Greenzhe](/user/552298) 阿哲。。。。。样例都过不了了，还有我不是标记了素数吗，如果写成$!vis[i]$那不就是判断合数
by gghack_Nythix @ 2022-12-26 15:26:57
@[gghack_m3d](/user/895690) 啊您标记的是非素数啊
```cpp
vis[0] = vis[1] = true;
```
如果还是错那就是其他问题了
by Greenzhe @ 2022-12-26 15:29:09
@[gghack_m3d](/user/895690) 筛子打错了。
```cpp
for(int j = i * i; j <= n;j += i)
{
vis[i] = true; //乐
}
```
by liangbowen @ 2022-12-26 15:30:34
@[liangbowen](/user/367488)
```cpp
#include <bits/stdc++.h>
using namespace std;
#define int long long
bool vis[10000005];
void prime(int n)
{
vis[0] = vis[1] = false;
for(int i = 2;i * i <= n;i ++)
{
if(!vis[i])
for(int j = i * i; j <= n;j += i)
{
vis[j] = true;
}
}
}
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n,m;
cin >> n >> m;
prime(m);
for(int i = 1;i <= n;i ++)
{
int l,r;
cin >> l >> r;
if(l < 1 || r > m)
{
cout << "Crossing the line" << endl;
}
else
{
int ans = 0;
for(int i = l;i <= r;i ++)
{
if(vis[i])
{
ans++;
}
}
cout << ans <<endl;
}
}
}
```这只对了一个点
by gghack_Nythix @ 2022-12-26 15:45:20
@[gghack_m3d](/user/895690) 为啥不看一眼Greenzhe的评论，你还是
```cpp
vis[0] = vis[1] = true;
```
就可以了。然后下面改成
```cpp
for(int i = l;i <= r;i ++)
{
if(!vis[i])
{
ans++;
}
}
```
by liangbowen @ 2022-12-26 15:49:41
@[liangbowen](/user/367488) 看了，现在改成标记非素数了最慢832ms然而还是有问题，只对了一个点
```cpp
#include <bits/stdc++.h>
using namespace std;
#define int long long
bool vis[10000005];
void prime(int n)
{
vis[0] = vis[1] = true;
for(int i = 2;i * i <= n;i ++)
{
if(!vis[i])
{
for(int j = i * i; j <= n;j += i)
{
vis[j] = true;
}
}
}
}
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n,m;
cin >> n >> m;
prime(m);
for(int i = 1;i <= n;i ++)
{
int l,r;
cin >> l >> r;
if(l < 1 || r > m)
{
cout << "Crossing the line" << endl;
continue;
}
int ans = 0;
for(int i = l;i <= r;i ++)
{
if(!vis[i])
{
ans++;
}
}
cout << ans <<endl;
}
}
```
by gghack_Nythix @ 2022-12-26 15:54:06
@[liangbowen](/user/367488) 本来想水一道题，结果还没过
by gghack_Nythix @ 2022-12-26 15:54:36
@[gghack_m3d](/user/895690) ？？？？？？？？我过了啊
by liangbowen @ 2022-12-26 15:55:11
@[liangbowen](/user/367488) 我说的是我
by gghack_Nythix @ 2022-12-26 15:55:50