View Compilation Error

0_0_25074589_694.cpp: In member function 'void Graph::Init(int)':
0_0_25074589_694.cpp:13:37: error: 'memset' was not declared in this scope
         memset(head, -1, 4 * (n + 1));  
                                     ^
0_0_25074589_694.cpp: In member function 'void Query::Init(int)':
0_0_25074589_694.cpp:29:37: error: 'memset' was not declared in this scope
         memset(head, -1, 4 * (n + 1));  
                                     ^