View Compilation Error

0_0_33553291_8260.cpp:16:1: error: 'vector' does not name a type
 vector<node> arr1[55];
 ^
0_0_33553291_8260.cpp: In function 'void initial()':
0_0_33553291_8260.cpp:20:9: error: 'arr1' was not declared in this scope
         arr1[i].clear();
         ^
0_0_33553291_8260.cpp: In function 'void dfs(int)':
0_0_33553291_8260.cpp:28:8: error: 'arr1' was not declared in this scope
     if(arr1[j].size() == 0){
        ^
0_0_33553291_8260.cpp:34:35: error: 'max' was not declared in this scope
             ans = max(ans, A*B*C*D);
                                   ^
0_0_33553291_8260.cpp:34:35: note: suggested alternative:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/algorithm:62:0,
                 from 0_0_33553291_8260.cpp:3:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algo.h:3454:5: note:   'std::max'
     max(initializer_list<_Tp> __l, _Compare __comp)
     ^
0_0_33553291_8260.cpp: In function 'int main()':
0_0_33553291_8260.cpp:51:13: error: 'arr1' was not declared in this scope
             arr1[e].push_back(n1[j]);
             ^