/in/foo.cc: In function 'void DFS(int)':
/in/foo.cc:28:9: error: 'dfs' was not declared in this scope
         dfs(num + 1) ;//深搜
         ^~~
/in/foo.cc:28:9: note: suggested alternative: 'ffs'
         dfs(num + 1) ;//深搜
         ^~~
         ffs