backtrack_binary_rc.cpp

# include <cstdlib>
# include <iomanip>
# include <iostream>
# include <ctime>

using namespace std;

# include "backtrack_binary_rc.hpp"

//****************************************************************************80

void backbin_rc ( int n, bool reject, int &n2, int choice[] )

//****************************************************************************80
//
//  Purpose:
//
//    BACKBIN_RC uses reverse communication for binary backtracking.
//
//  Discussion:
//
//    If this procedure returns a solution with N2 = N, which is acceptable
//    to the user, then a full solution has been found.
//
//    If this procedure returns N2 = -1, no more potential solutions are
//    available to consider.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license.
//
//  Modified:
//
//    01 January 2014
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int N, the length of the full solution.
//
//    Input, bool REJECT, is TRUE if the proposed partial solution
//    in the first N2 entries of CHOICE must be rejected.
//
//    Input/output, int &N2, the length of the current
//    partial solution.  On first call for a given problem, the user
//    should set N2 to -1.  If the program has exhausted the search space,
//    the value of N2 will be returned as -1.
//
//    Input/output, int CHOICE[N], indicates the current
//    partial solution in entries 1 through N2, which will contain 0 or 1.
//
{
  int i;
//
//  N2 = -1 means an initialization call.
//
  if ( n2 == -1 )
  {
    for ( i = 0; i < n; i++ )
    {
      choice[i] = -1;
    }
    n2 = 1;
    choice[n2-1] = 1;
  }
//
//  1 <= FOCUS means we asked the user to evaluate CHOICE(1:N2).
//
//  N2 = N means we returned a full prospective solution
//  so in any case we must increment CHOICE.
//
//  Returning REJECT = 1 means no solution begins this way
//  so we must increment CHOICE.
//
  else if ( n2 == n || reject )
  {
    while ( 1 < n2 )
    {
      if ( choice[n2-1] == 1 )
      {
        choice[n2-1] = 0;
        break;
      }
      choice[n2-1] = -1;
      n2 = n2 - 1;
    }
//
//  Have we exhausted the solution space?
//
    if ( n2 == 1 )
    {
      if ( choice[n2-1] == 1 )
      {
        choice[n2-1] = 0;
      }
      else
      {
        choice[n2-1] = -1;
        n2 = -1;
      }
    }
  }
//
//  N2 < N and not REJECT means we can increment N2.
//
  else
  {
    n2 = n2 + 1;
    choice[n2-1] = 1;
  }

  return;
}
//****************************************************************************80

int i4_power ( int i, int j )

//****************************************************************************80
//
//  Purpose:
//
//    I4_POWER returns the value of I^J.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license.
//
//  Modified:
//
//    01 April 2004
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int I, J, the base and the power.  J should be nonnegative.
//
//    Output, int I4_POWER, the value of I^J.
//
{
  int k;
  int value;

  if ( j < 0 )
  {
    if ( i == 1 )
    {
      value = 1;
    }
    else if ( i == 0 )
    {
      cerr << "\n";
      cerr << "I4_POWER - Fatal error!\n";
      cerr << "  I^J requested, with I = 0 and J negative.\n";
      exit ( 1 );
    }
    else
    {
      value = 0;
    }
  }
  else if ( j == 0 )
  {
    if ( i == 0 )
    {
      cerr << "\n";
      cerr << "I4_POWER - Fatal error!\n";
      cerr << "  I^J requested, with I = 0 and J = 0.\n";
      exit ( 1 );
    }
    else
    {
      value = 1;
    }
  }
  else if ( j == 1 )
  {
    value = i;
  }
  else
  {
    value = 1;
    for ( k = 1; k <= j; k++ )
    {
      value = value * i;
    }
  }
  return value;
}
//****************************************************************************80

void timestamp ( )

//****************************************************************************80
//
//  Purpose:
//
//    TIMESTAMP prints the current YMDHMS date as a time stamp.
//
//  Example:
//
//    31 May 2001 09:45:54 AM
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license.
//
//  Modified:
//
//    08 July 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    None
//
{
# define TIME_SIZE 40

  static char time_buffer[TIME_SIZE];
  const struct std::tm *tm_ptr;
  size_t len;
  std::time_t now;

  now = std::time ( NULL );
  tm_ptr = std::localtime ( &now );

  len = std::strftime ( time_buffer, TIME_SIZE, "%d %B %Y %I:%M:%S %p", tm_ptr );

  std::cout << time_buffer << "\n";

  return;
# undef TIME_SIZE
}