Compilare: user.cpp: In function ‘int solve(char*)’: user.cpp:12:27: warning: NULL used in arithmetic [-Wpointer-arith] for(int i = 0;s[i] != NULL;i++) ^ user.cpp:25:28: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] cop[j - i - 1] = NULL; ^ user.cpp:46:24: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] cop[j - i] = NULL; ^ user.cpp:60:12: warning: ‘x’ may be used uninitialized in this function [-Wmaybe-uninitialized] return x; ^ user.cpp:11:22: warning: ‘nr’ may be used uninitialized in this function [-Wmaybe-uninitialized] int x , sens,k ,nr,j; char cop[100002]; bool ok = false; ^