View Compilation Error

0_0_18382936_16115.cpp: In function 'double solve(const std::vector<Point>&, int, int)':
0_0_18382936_16115.cpp:53:10: error: 'DBL_MAX' was not declared in this scope
   return DBL_MAX;
          ^
0_0_18382936_16115.cpp:64:27: error: 'cmpy' was not declared in this scope
  sort(b.begin(), b.end(), cmpy);
                           ^
0_0_18382936_16115.cpp: In function 'int main()':
0_0_18382936_16115.cpp:81:28: error: 'cmpx' was not declared in this scope
   sort(a.begin(), a.end(), cmpx);
                            ^