View Compilation Error

0_0_33880742_26926.cpp: In function 'bool solve()':
0_0_33880742_26926.cpp:52:3: error: reference to 'hash' is ambiguous
   hash(sta[i]);
   ^
0_0_33880742_26926.cpp:21:6: note: candidates are: void hash(int)
 void hash(int len){
      ^
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/basic_string.h:3068:0,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/string:52,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/random:40,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algo.h:66,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/algorithm:62,
                 from 0_0_33880742_26926.cpp:2:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/functional_hash.h:58:12: note:                 template<class _Tp> struct std::hash
     struct hash;
            ^