Compilare: main.cpp: In function 'int main()': main.cpp:19:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); i++) ~^~~~~~~~~ main.cpp:27:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); i++) ~^~~~~~~~~ main.cpp:31:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=i+1; j<s.size(); j++) ~^~~~~~~~~