View Compilation Error

0_0_18028630_15371.cpp: In function 'void Ins(char*, int)':
0_0_18028630_15371.cpp:21:46: error: 'memset' was not declared in this scope
              memset(chd[sz],0,sizeof(chd[sz]));               
                                              ^
0_0_18028630_15371.cpp: In function 'void solve()':
0_0_18028630_15371.cpp:55:29: error: 'memset' was not declared in this scope
     memset(dp1,0,sizeof(dp1));  
                             ^
0_0_18028630_15371.cpp: In function 'int main(int, char**)':
0_0_18028630_15371.cpp:94:41: error: 'memset' was not declared in this scope
           memset(chd[0],0,sizeof(chd[0]));
                                         ^