Compilare: main.cpp: In function 'int main()': main.cpp:24:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (k<C[i].size() && k<C[j].size() && !ok){ ~^~~~~~~~~~~~ main.cpp:24:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (k<C[i].size() && k<C[j].size() && !ok){ ~^~~~~~~~~~~~