Compilare: main.cpp: In function 'int main()': main.cpp:34:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); ++i) { ~~^~~~~~~~~~ main.cpp:41:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < a.size(); ++i) { ~~^~~~~~~~~~ main.cpp:51:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = (int)a.size(); i < b.size(); ++i) { ~~^~~~~~~~~~