Compilare: main.cpp: In function 'int main()': main.cpp:69:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); ++i) ~~^~~~~~~~~~ main.cpp:74:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < s.size(); ++i) { ~~^~~~~~~~~~