Compilare: main.cpp: In function 'int main()': main.cpp:41:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a.size()-1;i++) ~^~~~~~~~~~~ main.cpp:42:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=i+1;j<a.size();j++){ ~^~~~~~~~~ main.cpp:48:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=1; i<s.size(); i++){ ~^~~~~~~~~