Compilare: main.cpp:2:0: warning: ignoring #pragma gcc optimize [-Wunknown-pragmas] #pragma gcc optimize("O3"); main.cpp: In function 'int main()': main.cpp:36:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i1 <= v[i].size() - 1 && j1 <= v[j].size() -1 ) ~~~^~~~~~~~~~~~~~~~~~ main.cpp:36:55: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i1 <= v[i].size() - 1 && j1 <= v[j].size() -1 ) ~~~^~~~~~~~~~~~~~~~~ main.cpp:43:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i1 == v[i].size()) ~~~^~~~~~~~~~~~~~