View Compilation Error

0_0_36957638_8294.cpp: In function 'node mymut(node, node)':
0_0_36957638_8294.cpp:11:34: error: 'memset' was not declared in this scope
  memset(sum.arr,0,sizeof(sum.arr));
                                  ^
0_0_36957638_8294.cpp: In function 'node ksm(node, ll)':
0_0_36957638_8294.cpp:24:34: error: 'memset' was not declared in this scope
  memset(ans.arr,0,sizeof(ans.arr));
                                  ^