View Compilation Error

0_0_25697318_28713.cpp: In function 'void updatenode(node&, node&)':
0_0_25697318_28713.cpp:33:34: error: 'memset' was not declared in this scope
  memset(res.dp, 0, sizeof(res.dp));
                                  ^
0_0_25697318_28713.cpp: In function 'node merge(node&, node&)':
0_0_25697318_28713.cpp:48:34: error: 'memset' was not declared in this scope
  memset(res.dp, 0, sizeof(res.dp));
                                  ^
0_0_25697318_28713.cpp: In function 'int newnode(int)':
0_0_25697318_28713.cpp:114:56: error: 'memset' was not declared in this scope
  memset(tree[nodenum].num, 0, sizeof(tree[nodenum].num));
                                                        ^