View Compilation Error

0_0_18078417_4654.cpp: In function 'int BFS(int, int)':
0_0_18078417_4654.cpp:14:32: error: 'memset' was not declared in this scope
     memset(pre, -1, sizeof(pre));
                                ^
0_0_18078417_4654.cpp: In function 'int main()':
0_0_18078417_4654.cpp:67:28: error: 'memset' was not declared in this scope
      memset(r, 0, sizeof(r));
                            ^