View Compilation Error

0_0_17813422_13812.cpp: In function 'void bfs()':
0_0_17813422_13812.cpp:7:38: error: 'memset' was not declared in this scope
 #define cls(a,b) memset(a,b,sizeof(a))
                                      ^
0_0_17813422_13812.cpp:27:2: note: in expansion of macro 'cls'
  cls(vi,0);
  ^