View Compilation Error

0_0_20029065_18781.cpp: In function 'void bfs()':
0_0_20029065_18781.cpp:14:29: error: 'memset' was not declared in this scope
  memset(pre, -1, sizeof(pre));
                             ^
0_0_20029065_18781.cpp: In function 'int main()':
0_0_20029065_18781.cpp:48:31: error: 'memset' was not declared in this scope
   memset(flow, 0, sizeof(flow));
                               ^