DZone Snippets: intersection code

Full intersection between 2 arrays

gaspode () — Fri, 02 Jun 2006 01:32:53 GMT

// This snippet adds a method to Array to perform a full intersection between 2 arrays. The & method eliminates duplicate objects, this doesn't!



class Array

  def real_intersection(arr2)

    self_sorted = self.sort

    target_sorted = arr2.sort

    intersection= []

    jstart=0

    for i in (0..self_sorted.length-1)

      for j in (jstart..target_sorted.length-1)

        if self_sorted[i] == target_sorted[j]

          jstart = j+1

          intersection[intersection.length] = self_sorted[i]

          break

        end

      end

    end

    return intersection

  end

end

// tests



require 'test/unit'



class ArrayIntersectionTests < Test::Unit::TestCase    

  def test_real_array_intersection

    assert_equal [2], [2, 2, 2, 3, 7, 13, 49] & [2, 2, 2, 5, 11, 107]

    assert_equal [2, 2, 2], [2, 2, 2, 3, 7, 13, 49].real_intersection([2, 2, 2, 5, 11, 107])

    assert_equal ['a', 'c'], ['a', 'b', 'a', 'c'] & ['a', 'c', 'a', 'd']

    assert_equal ['a', 'a', 'c'], ['a', 'b', 'a', 'c'].real_intersection(['a', 'c', 'a', 'd'])

  end

end

Line intersection

eskimoblood () — Tue, 23 May 2006 11:19:02 GMT

the function gives the point where 2 lines intersect



float[] checkIntersection(float lineAx1,float lineAy1,float lineAx2,float lineAy2,float lineBx1,float lineBy1,float lineBx2,float lineBy2){

  float aM, bM, aB, bB, isX=0, isY=0;

  if((lineAx2-lineAx1)==0){

    isX=lineAx1;

    bM=(lineBy2-lineBy1)/(lineBx2-lineBx1);

    bB=lineBy2-bM*lineBx2;

    isY=bM*isX+bB;

  }

  else if((lineBx2-lineBx1)==0){

    isX=lineBx1;

    aM=(lineAy2-lineAy1)/(lineAx2-lineAx1);

    aB=lineAy2-aM*lineAx2;

    isY=aM*isX+aB;

  }

  else{

    aM=(lineAy2-lineAy1)/(lineAx2-lineAx1);

    bM=(lineBy2-lineBy1)/(lineBx2-lineBx1);

    aB=lineAy2-aM*lineAx2;

    bB=lineBy2-bM*lineBx2;

    isX=max(((bB-aB)/(aM-bM)),0);

    isY=aM*isX+aB;

  }

  float[] r={

    isX,isY  };

  return r; 

}

Lenght between a dot and a line //JavaScript Function

jonasraoni (Jonas Raoni Soares Silva) — Fri, 09 Sep 2005 05:01:25 GMT

Given a dot and a line, it returns the distance between them, the last parameter tells if the line should be considered infinite or if the function should respect its limits.

[UPDATED CODE AND HELP CAN BE FOUND HERE]



//+ Jonas Raoni Soares Silva

//@ http://jsfromhell.com/math/dot-line-length [v1.0]



dotLineLength = function( x, y, x0, y0, x1, y1, o ){

	function lineLength( x, y, x0, y0 ){

		return Math.sqrt( ( x -= x0 ) * x + ( y -= y0 ) * y );

	}

	if( o && !( o = function( x, y, x0, y0, x1, y1 ){

		if( !( x1 - x0 ) ) return { x: x0, y: y };

		else if( !( y1 - y0 ) ) return { x: x, y: y0 };

		var left, tg = -1 / ( ( y1 - y0 ) / ( x1 - x0 ) );

		return { x: left = ( x1 * ( x * tg - y + y0 ) + x0 * ( x * - tg + y - y1 ) ) / ( tg * ( x1 - x0 ) + y0 - y1 ), y: tg * left - tg * x + y };

	}( x, y, x0, y0, x1, y1 ), o.x >= Math.min( x0, x1 ) && o.x <= Math.max( x0, x1 ) && o.y >= Math.min( y0, y1 ) && o.y <= Math.max( y0, y1 ) ) ){

		var l1 = lineLength( x, y, x0, y0 ), l2 = lineLength( x, y, x1, y1 );

		return l1 > l2 ? l2 : l1;

	}

	else {

		var a = y0 - y1, b = x1 - x0, c = x0 * y1 - y0 * x1;

		return Math.abs( a * x + b * y + c ) / Math.sqrt( a * a + b * b );

	}

};

"Intersection dot" between a dot and a line //JavaScript Function

jonasraoni (Jonas Raoni Soares Silva) — Fri, 09 Sep 2005 04:58:55 GMT

Given a line and a dot, it return the coordinates of their intersection.

[UPDATED CODE AND HELP CAN BE FOUND HERE]



//+ Jonas Raoni Soares Silva

//@ http://jsfromhell.com/math/dot-line-intersection [v1.0]



dotLineIntersection = function( x, y, x0, y0, x1, y1 ){

	if( !( x1 - x0 ) )

		return { x: x0, y: y };

	else if( !( y1 - y0 ) )

		return { x: x, y: y0 };

	var left, tg = -1 / ( ( y1 - y0 ) / ( x1 - x0 ) );

	return { x: left = ( x1 * ( x * tg - y + y0 ) + x0 * ( x * - tg + y - y1 ) ) / ( tg * ( x1 - x0 ) + y0 - y1 ), y: tg * left - tg * x + y };

};