View Compilation Error

0_0_21925137_4393.cpp: In function 'void init()':
0_0_21925137_4393.cpp:22:34: error: 'memset' was not declared in this scope
     memset(head, -1, sizeof(head));
                                  ^
0_0_21925137_4393.cpp: In function 'int main()':
0_0_21925137_4393.cpp:89:35: error: 'memset' was not declared in this scope
         memset(vis, 0, sizeof(vis));
                                   ^