> I’m a Chinese. Sorry if my English had some grammar mistakes.↵
↵
---↵
↵
In a recent contest: [contest:1829], I saw a **“Successful hacking attempt”** in the **“Hacks”** list. But I think this hacking might involve cheating.↵
↵
Look at this hacked submission: [submission:204925830].↵
↵
The source code of the defender contained a **“landmine”**, which means that for some corner case (unlikely contained in test data), the code wouldn’t be accepted, which is intentionally designed for hackers.↵
↵
Following is the source code (GNU C++14). Note the corner case in the code that would make it wrong.↵
↵
---↵
↵
```cpp↵
#include <algorithm>↵
#include <iostream>↵
#include <cstring>↵
#include <cstdio>↵
#include <vector>↵
#include <cmath>↵
#include <queue>↵
#include <stack>↵
#include <set>↵
#include <map>↵
↵
using namespace std;↵
↵
string s1,s2;↵
int t;↵
↵
int main(){↵
scanf("%d",&t);↵
s1 = "codeforces";↵
int ans;↵
while(t --){↵
cin >> s2;↵
if(s2 == "xxxxxxxxxx"){ // Here! The corner case↵
puts("-1"); // Wrong output↵
return 0;↵
}↵
ans = 0;↵
for(unsigned int i = 0 ; i < s1.size() ; ++i){↵
if(s1[i] != s2[i])↵
++ans;↵
}↵
printf("%d\n",ans);↵
}↵
return 0;↵
}↵
```↵
↵
---↵
↵
Therefore, for the case “`xxxxxxxxxx`”, the code would definitely get **“Wrong answer”**. Unluckily (or luckily, for the hacker), this corner case wasn’t contained in test data.↵
↵
Then view the hacking test.↵
↵
---↵
↵
```↵
1↵
xxxxxxxxxx↵
```↵
↵
---↵
↵
What a “coincidence”!↵
↵
But do you think someone may intentionally leave a “landmine” for others to hack, and give himself/herself a chance to lose $50$ points? Anyone knows it’s impossible.↵
↵
And see the rating of the defender: Newbie. I’m not discriminating against Newbies (since so am I), but this is one of the typical features of an alt account. In addition, he/she participated in few contests so far.↵
↵
So, most likely, the contestant created an **alt account**, used his/her alt account to submit a “landmine code”, used his/her main account to hack it, to let the main account get extra $100$ points. Or maybe, it’s his/her friend, not his/her alt account. But that doesn’t matter.↵
↵
This is why I suspect that this hacking may involve cheating.↵
↵
---↵
↵
I’m not targetting any user. This example is just one of all. Actually I saw at least three such examples of “landmine code” hackings only in this contest (where some of the defenders are even Unrated).↵
↵
Cheating is shameful, but a flawed rule may also become a breeding ground for cheating behaviors. I think this phenomenon should be controlled.
↵
---↵
↵
In a recent contest: [contest:1829], I saw a **“Successful hacking attempt”** in the **“Hacks”** list. But I think this hacking might involve cheating.↵
↵
Look at this hacked submission: [submission:204925830].↵
↵
The source code of the defender contained a **“landmine”**, which means that for some corner case (unlikely contained in test data), the code wouldn’t be accepted, which is intentionally designed for hackers.↵
↵
Following is the source code (GNU C++14). Note the corner case in the code that would make it wrong.↵
↵
---↵
↵
```cpp↵
#include <algorithm>↵
#include <iostream>↵
#include <cstring>↵
#include <cstdio>↵
#include <vector>↵
#include <cmath>↵
#include <queue>↵
#include <stack>↵
#include <set>↵
#include <map>↵
↵
using namespace std;↵
↵
string s1,s2;↵
int t;↵
↵
int main(){↵
scanf("%d",&t);↵
s1 = "codeforces";↵
int ans;↵
while(t --){↵
cin >> s2;↵
if(s2 == "xxxxxxxxxx"){ // Here! The corner case↵
puts("-1"); // Wrong output↵
return 0;↵
}↵
ans = 0;↵
for(unsigned int i = 0 ; i < s1.size() ; ++i){↵
if(s1[i] != s2[i])↵
++ans;↵
}↵
printf("%d\n",ans);↵
}↵
return 0;↵
}↵
```↵
↵
---↵
↵
Therefore, for the case “`xxxxxxxxxx`”, the code would definitely get **“Wrong answer”**. Unluckily (or luckily, for the hacker), this corner case wasn’t contained in test data.↵
↵
Then view the hacking test.↵
↵
---↵
↵
```↵
1↵
xxxxxxxxxx↵
```↵
↵
---↵
↵
What a “coincidence”!↵
↵
But do you think someone may intentionally leave a “landmine” for others to hack, and give himself/herself a chance to lose $50$ points? Anyone knows it’s impossible.↵
↵
And see the rating of the defender: Newbie. I’m not discriminating against Newbies (since so am I), but this is one of the typical features of an alt account. In addition, he/she participated in few contests so far.↵
↵
So, most likely, the contestant created an **alt account**, used his/her alt account to submit a “landmine code”, used his/her main account to hack it, to let the main account get extra $100$ points. Or maybe, it’s his/her friend, not his/her alt account. But that doesn’t matter.↵
↵
This is why I suspect that this hacking may involve cheating.↵
↵
---↵
↵
I’m not targetting any user. This example is just one of all. Actually I saw at least three such examples of “landmine code” hackings only in this contest (where some of the defenders are even Unrated).↵
↵
Cheating is shameful, but a flawed rule may also become a breeding ground for cheating behaviors. I think this phenomenon should be controlled.
