Like I want it to be n X m size. How to do it?

Here are two submission — Accepted_one || Compilation_error_one. I don't understand why strstr is behaving different in those two solutions?

Question: http://codeforces.com/contest/1004/problem/D Ideone solution: https://ideone.com/ntZyd6 Codeforces solution: http://codeforces.com/contest/1004/submission/40031007

I can't figure this out. Any help would be appreciated.