# include <float.h>
# include <math.h>
# include <stdlib.h>

# include "closest_pair_brute.h"

/******************************************************************************/

void closest_pair_brute ( int n, double xy[], double *d, int *i, int *j )

/******************************************************************************/
/*
  Purpose:

    closest_pair_brute() finds closest pair of points in 2d using brute force.

  License:

    This code is distributed under the MIT license.

  Modified:

    03 April 2024

  Author:

    Original MATLAB code by Cleve Moler.
    This version by John Burkardt.

  Reference:

    Cleve Moler,
    https://blogs.mathworks.com/cleve/2024/03/28/closest-pair-of-points-problem/
    Closest pair of points problem,
    28 March 2024.

  Input:

    int n: the number of points.

    double xy(n,2): the X and Y coordinates of the points.

  Output:

    double d: the distance of the closest pair.

    int i, j: the indices of the closest pair.
*/
{
  double d2;
  int i2;
  int j2;

  *d = HUGE_VAL;
  *i = -1;
  *j = -1;

  for ( i2 = 0; i2 < n; i2++ )
  {
    for ( j2 = i2 + 1; j2 < n; j2++ )
    {
      d2 = pow ( xy[i2+0*n] - xy[j2+0*n], 2 )
         + pow ( xy[i2+1*n] - xy[j2+1*n], 2 );
      d2 = sqrt ( d2 );
      if ( d2 < *d )
      {
        *d = d2;
        *i = i2;
        *j = j2;
      }
    }
  }

  return;
}