Compilare: user.cpp: In function ‘int main()’: user.cpp:138:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] mat[i][e]=NULL; ^ user.cpp:139:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] mat[j][w]=NULL; ^ user.cpp:162:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] mat[i][e]=NULL; ^ user.cpp:163:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] mat[j][w]=NULL; ^ user.cpp:37:15: warning: unused variable ‘l’ [-Wunused-variable] int i,j,k,l,m,z,ok,p,ua,d,w,e,q,u,o,aux,n,t; ^ user.cpp:37:17: warning: unused variable ‘m’ [-Wunused-variable] int i,j,k,l,m,z,ok,p,ua,d,w,e,q,u,o,aux,n,t; ^ user.cpp:37:47: warning: unused variable ‘t’ [-Wunused-variable] int i,j,k,l,m,z,ok,p,ua,d,w,e,q,u,o,aux,n,t; ^ user.cpp:60:10: warning: ‘ok’ may be used uninitialized in this function [-Wmaybe-uninitialized] if(ok==1) {k++;ok=0;} ^