View Compilation Error

0_0_34282744_26218.cpp: In function 'void init()':
0_0_34282744_26218.cpp:18:30: error: 'memset' was not declared in this scope
  memset(head, 0, sizeof(head));
                              ^
0_0_34282744_26218.cpp: In function 'void c1::init()':
0_0_34282744_26218.cpp:47:31: error: 'memset' was not declared in this scope
   memset(head, 0, sizeof(head));
                               ^