Compilare: user.cpp: In function ‘int main()’: user.cpp:131:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] mat[i][e]=NULL; ^ user.cpp:132:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] mat[j][w]=NULL; ^ user.cpp:154:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] mat[i][e]=NULL; ^ user.cpp:155:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] mat[j][w]=NULL; ^ user.cpp:168:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] mat[j][0]=NULL; ^ user.cpp:178:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<strlen(mat[i]);j++) ^ user.cpp:184:21: warning: NULL used in arithmetic [-Wpointer-arith] if(mat[i][0]!=NULL) ^ user.cpp:38:15: 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:38:17: 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:61:10: warning: ‘ok’ may be used uninitialized in this function [-Wmaybe-uninitialized] if(ok==1) {k++;ok=0;} ^