View Compilation Error

0_0_18803155_14602.cpp: In function 'void Insert(std::string)':
0_0_18803155_14602.cpp:22:42: error: 'memset' was not declared in this scope
             memset(&tree[sz],0,sizeof(sz));
                                          ^
0_0_18803155_14602.cpp: In function 'int main()':
0_0_18803155_14602.cpp:44:35: error: 'memset' was not declared in this scope
     memset(&tree[0],0,sizeof(Trie));
                                   ^