View Compilation Error

0_0_16921060_17781.cpp: In function 'bool cmp(ST, ST)':
0_0_16921060_17781.cpp:13:23: error: 'strcmp' was not declared in this scope
  return strcmp(a.s,b.s) < 0 ? true : false;
                       ^
0_0_16921060_17781.cpp: In function 'int main(int, char**)':
0_0_16921060_17781.cpp:27:24: error: 'memset' was not declared in this scope
  memset(st,0,sizeof(st));
                        ^
0_0_16921060_17781.cpp:48:23: error: 'sort' was not declared in this scope
   sort(st+1,st+n+1,cmp);
                       ^