View Compilation Error

0_0_22077973_25042.cpp: In function 'void build()':
0_0_22077973_25042.cpp:62:30: error: 'memset' was not declared in this scope
  memset(tree, 0, sizeof(tree));
                              ^
0_0_22077973_25042.cpp: In function 'void init()':
0_0_22077973_25042.cpp:12:38: error: 'memset' was not declared in this scope
 #define mem(a,b) memset(a,b,sizeof(a))
                                      ^
0_0_22077973_25042.cpp:111:2: note: in expansion of macro 'mem'
  mem(head, -1);
  ^