View Compilation Error

0_0_33483543_24234.cpp: In function 'int main()':
0_0_33483543_24234.cpp:26:32: error: 'memset' was not declared in this scope
   memset(head, -1, sizeof(head));
                                ^
0_0_33483543_24234.cpp: In function 'll bfs()':
0_0_33483543_24234.cpp:63:29: error: 'memset' was not declared in this scope
  memset(pre, -1, sizeof(pre));
                             ^