foo.cc: In function 'void DFS(int, int)':
foo.cc:60:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < edge[x].son.size(); i++)
                         ~~^~~~~~~~~~~~~~~~~~~~
foo.cc: In function 'void FindDFS(int)':
foo.cc:76:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < edge[x].son.size(); i++)
                         ~~^~~~~~~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:92:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~
foo.cc:94:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&edge[i].num);
         ~~~~~^~~~~~~~~~~~~~~~~~~
foo.cc:98:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d%d", &x, &y, &z);
         ~~~~~^~~~~~~~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。