Compilare: main.cpp: In function 'int main()': main.cpp:37:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (pos1 < L[i].size() && pos2 < L[j].size()){ ~~~~~^~~~~~~~~~~~~ main.cpp:37:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (pos1 < L[i].size() && pos2 < L[j].size()){ ~~~~~^~~~~~~~~~~~~ main.cpp:48:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (;pos1<L[i].size();++pos1) ~~~~^~~~~~~~~~~~ main.cpp:51:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (;pos2<L[j].size();++pos2) ~~~~^~~~~~~~~~~~