How to know the contest id of a contest ?

why this code is failing for problem C 150995742

Why this code is failing 150995742 for problem C. I've used same approach as in tutorial, but not able to figure out mistake inside for loop.

In div2B why the counterpart of x is m-x. If m=5 and x=13 then counterpart of x will be 5-13 = -8 but we know that we need only 2 to add to 13 to make their sum divisible by 5. Instead it should be m-(x%m). Can anyone tell whether I'm correct or going wrong ??

Can anyone help what is wrong with this code ?111115251

Can anyone explain this line in editorial of div2 B "In this array the amount of x and the amount of m−x should differ not more than by 1, that's why we need to make max(0,|cntx−cntm−x|−1) arrays, containing a single number (x or m−x) that is more common."

Can anyone tell why this code gives runtime error for second test case 109327282

Can anyone tell what is wrong with this method in Problem A 108325761

How did you debug so fast... I'm a beginner and often unable to find out mistake in my own code and often waste much time finding out mistakes, please tell how to do that

Can someone tell why it is giving wrong output 107936839

Can anyone tell what's wrong with this code, it is giving wrong answer for test case 3. https://codeforces.me/contest/1440/submission/102106895

Can anyone tell why thus code is failing for 1234567890 https://codeforces.me/contest/1465/submission/101931003