Compilare: user.cpp: In function ‘int main()’: user.cpp:76:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < P[i].size(); ++ j) ^ user.cpp:80:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < P[i - DX].size(); ++ j) ^ user.cpp:90:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < P[i].size(); ++ j) ^ user.cpp:94:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < P[i + DX].size(); ++ j) ^