View Compilation Error

0_0_13655488_30909.cpp: In function 'void insert(char*)':
0_0_13655488_30909.cpp:23:54: error: 'memset' was not declared in this scope
             memset(qq[k].nxt, NULL, sizeof(qq[k].nxt));
                                                      ^
0_0_13655488_30909.cpp: In function 'int main()':
0_0_13655488_30909.cpp:92:46: error: 'memset' was not declared in this scope
         memset(rt->nxt, NULL, sizeof(rt->nxt));
                                              ^