View Compilation Error

0_0_39002766_22323.cpp: In member function 'void graph::init(int)':
0_0_39002766_22323.cpp:15:25: error: 'memset' was not declared in this scope
   15 |                         memset(head, 0, n + 1 << 2);
      |                         ^~~~~~
0_0_39002766_22323.cpp:3:1: note: 'memset' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    2 | #include <iostream>
  +++ |+#include <cstring>
    3 | using namespace std;