View Compilation Error

0_0_16981434_19310.cpp: In function 'bool BFS(int, int)':
0_0_16981434_19310.cpp:47:31: error: 'memset' was not declared in this scope
     memset(used,0,sizeof(used));
                               ^
0_0_16981434_19310.cpp: In function 'int Maxflow(int, int)':
0_0_16981434_19310.cpp:95:29: error: 'memset' was not declared in this scope
     memset(gap,0,sizeof(gap));
                             ^
0_0_16981434_19310.cpp: In function 'int main()':
0_0_16981434_19310.cpp:165:35: error: 'memset' was not declared in this scope
         memset(deep,0,sizeof(deep));
                                   ^