In this problem: 1364E - X-OR ,the discription said "Exit immediately after receiving −1 and you will see wrong answer verdict. Otherwise, you can get an arbitrary verdict because your solution will continue to read from a closed stream." .
And in this submission 83742870, I followed this instruction by using if(val==-1)return 0;(in line 53,67,68,84), and I got a "wrong answer" . But after that ,I change the sentence from if(val==-1)return 0; to 'if(val1==-1){while(1);return 0;}' , and I got a "Accept" 83742993.
I have no idea what is going on.....
Your solution is non-determenistic, verdicts can change without any changes in the code.
That is true. But i submited the same code 5 times before changing that sentences, and 5 times after changing that sentences. All my submission before changing get"wrong answer", and all my submission after changing get "accept" . You can see my submission for more detail QWQ
Yes, that is strange. But with fixed randseed both variants fail the same test (one by WA and one by TL).
OK, I give up :)
I have an idea though: As far as I know, Codeforces reruns a submit several times if it gets TL, so maybe this technic significantly increases the probability of success by abusing Codeforces generousity.
Let's say that probability to fail a test is $$$p=10^{-3}$$$. It is not good since we have around 100 tests. But if on fail solution gets TL, and then rerun two times, and to pass a test you only have to do it once, then probability to fail a test is $$$p^3=10^{-9}$$$ which is much better.
I agree with you. thx~
I wrote a blog about this exact thing just now. In my blog I came to the same conclusion that Um_nik wrote in his comment.
thx~