@jinxonik / UniLecs #201

spec_sum.cpp

#include <iostream>

using namespace std;

// Returns -1 for illegal source number (n)
int spec_sum(int n)
{
  if (n < 100 || n > 999) return -1;
  int a = n/100, b = n/10%10, c = n%10;
  if (b+c == 0) return n*2;
  int mn = min(a,min(b,c)), mx = max(a,max(b,c));
  if (mn == 0) return (a+b+c)*110 - mx*9;  // (a+b+c-mx)*110 + mx*101
  return (mn+mx)*81 + (a+b+c)*20;  // (mn+mx)*101 + (a+b+c-mn-mx)*20
}

int main()
{
  cout << spec_sum( 99) << endl;  // -1
  cout << spec_sum(100) << endl;  // 100+100=200
  cout << spec_sum(800) << endl;  // 800+800=1600
  cout << spec_sum(504) << endl;  // 405+540=945
  cout << spec_sum(709) << endl;  // 709+970=1679
  cout << spec_sum(413) << endl;  // 134+431=565
  cout << spec_sum(997) << endl;  // 799+997=1796
}