/* Solution to Topcoder SRM 351, D1, 250-Pointer: CoinsExchange.
   James S. Plank
   September, 2020
   Please see lecture notes in http://web.eecs.utk.edu/~plank/plank/classes/cs302/Notes/Recursion-Review/index.html for explanation.
 */

#include "coins_exchange.hpp"
#include <string>
#include <cstdio>
#include <cstdlib>
#include <iostream>
using namespace std;

int CE2(int G, int S, int B)
{
  printf("CE2: G:%d S:%d B:%d\n", G, S, B);

  printf("#1: Do we need gold? (recurse on yes)\n");
  /*----------------------------------------------------------------------- */
  /* #1: Do we need gold?   Yes = Add to our silver needs and do recursion.
                             No = keep going.  */

  if (G > 0) return G + CE2(0, S+G*11, B);

  printf("#2: Do we need bronze? (recurse on yes)\n");
  /*----------------------------------------------------------------------- */
  /* #2: Do we need bronze? Yes = Add to our silver needs and do recursion.
                            No  = keep going. */

  if (B > 0) return (B+8)/9 + CE2(G, S+(B+8)/9, 0);

  printf("#3: Do we have enough silver? (return on yes)\n");
  /*----------------------------------------------------------------------- */
  /* #3: Do we need silver?  No = return 0.
                            Yes = keep going. */

  if (S <= 0) return 0;

  printf("#4: Do we have enough gold for silver (return on yes)?\n");
  /*----------------------------------------------------------------------- */
  /* #4: Do we have enough gold to get all of our silver?
                         Yes = Satisfy silver from gold and return.
                          No = keep going. */

  if (-(G*9) >= S) return (S+8)/9;

  printf("#5: Do we have any gold for silver (recurse on yes)?\n");
  /*----------------------------------------------------------------------- */
  /* #5: Do we have any gold?  Yes = Use all of our gold for silver, and recurse.
                                No = keep going. */

  if (G < 0) return -G + CE2(0, S-(-G*9), B);

  printf("#6: Do we have enough bronze for silver? (return on yes). \n");
  /*----------------------------------------------------------------------- */
  /* #6: Do we have enough bronze to meet our silver needs?
                         Yes = Satisfy silver from bronze and return.
                          No = keep going. */

  if (-B >= S*11) return S;

  printf("#7: Failure -- return -100000000\n");

  return -1000000000; 
}


int CoinsExchange::countExchanges(int G1, int S1, int B1, int G2, int S2, int B2)
{
  int rv;

  rv = CE2(G2-G1, S2-S1, B2-B1);
  return (rv >= 0) ? rv : -1;
}