Compilare: user.cpp: In function ‘void dfs1(int)’: user.cpp:24:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a[k].size();i++) ^ user.cpp: In function ‘void dfs2(int)’: user.cpp:32:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<b[k].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:56:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<c[i].size();j++) ^