View Compilation Error

0_0_17133072_6194.cpp: In function 'int main()':
0_0_17133072_6194.cpp:21:27: error: 'memset' was not declared in this scope
   memset(cnt,0,sizeof(cnt));
                           ^
0_0_17133072_6194.cpp:24:13: error: 'sort' was not declared in this scope
   sort(b,b+n);
             ^
0_0_17133072_6194.cpp:25:24: error: 'unique' was not declared in this scope
   int sz = unique(b,b+n)-b;
                        ^