View Compilation Error

0_0_17332409_1587.cpp: In function 'void build(int, int, int)':
0_0_17332409_1587.cpp:35:31: error: 'memset' was not declared in this scope
   memset(v[rt],0,sizeof(v[rt]));
                               ^
0_0_17332409_1587.cpp: In function 'void update(int, int, int, int, int)':
0_0_17332409_1587.cpp:69:31: error: 'memset' was not declared in this scope
   memset(v[rt],0,sizeof(v[rt]));
                               ^