Compilare: main.cpp: In function 'int main()': main.cpp:38:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=a.size()-1; i>=a.size()-sol1; i--) ~^~~~~~~~~~~~~~~ main.cpp:45:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0; j<v[i].size(); j++) cout << v[i][j] << ' '; ~^~~~~~~~~~~~ main.cpp:48:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=1; j<v[i].size(); j++) sol2 = sol2 + (v[i][j] - v[i][j-1]) * val, val = 1 - val; ~^~~~~~~~~~~~