Compilare: main.cpp: In function 'int main()': main.cpp:22:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++) ~~^~~~~~~~~~ main.cpp:33:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i == s.size() - 1) ~~^~~~~~~~~~~~~~~ main.cpp:41:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++) ~~^~~~~~~~~~ main.cpp:52:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i == s.size() - 1) ~~^~~~~~~~~~~~~~~