Compilare: user.cpp: In function ‘void add_edges(int, int)’: user.cpp:21:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v1.size();i++) ~^~~~~~~~~~ user.cpp:22:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=i+1;j<v1.size();j++) ~^~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:61:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v1.size();i++) ~^~~~~~~~~~ user.cpp:62:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<v2.size();j++) ~^~~~~~~~~~