foo.cc: In function 'void tarjan(int)':
foo.cc:18:43: error: reference to 'hash' is ambiguous
  int v;DFN[u]=++idx;LOW[u]=idx;s1.push(u);hash[u]=1;
                                           ^~~~
foo.cc:15:24: note: candidates are: int hash [50010]
 int cnt,idx,head[maxn],hash[maxn];
                        ^~~~
In file included from /usr/include/c++/7/bits/basic_string.h:6587:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/functional_hash.h:58:12: note:                 template<class _Tp> struct std::hash
     struct hash;
            ^~~~
foo.cc:23:17: error: reference to 'hash' is ambiguous
         else if(hash[v]) LOW[u]=min(LOW[u],DFN[v]);
                 ^~~~
foo.cc:15:24: note: candidates are: int hash [50010]
 int cnt,idx,head[maxn],hash[maxn];
                        ^~~~
In file included from /usr/include/c++/7/bits/basic_string.h:6587:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/functional_hash.h:58:12: note:                 template<class _Tp> struct std::hash
     struct hash;
            ^~~~
foo.cc:28:33: error: reference to 'hash' is ambiguous
             v=s1.top();s1.pop();hash[v]=0;
                                 ^~~~
foo.cc:15:24: note: candidates are: int hash [50010]
 int cnt,idx,head[maxn],hash[maxn];
                        ^~~~
In file included from /usr/include/c++/7/bits/basic_string.h:6587:0,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/functional_hash.h:58:12: note:                 template<class _Tp> struct std::hash
     struct hash;
            ^~~~
foo.cc: In function 'int main()':
foo.cc:37:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n,&m);
  ~~~~~^~~~~~~~~~~~~~
foo.cc:40:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&u,&v);
   ~~~~~^~~~~~~~~~~~~~

正在同步测试数据，请稍后
自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。