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colinear.java
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colinear.java
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import java.awt.Point;
public class colinear {
public void swap(double[] array, int swp1, int swp2){
double temp = array[swp1];
array[swp1] = array[swp2];
array[swp2] = temp;
}
public int getPivot(double []array, int start, int end){
int pivot;
int middle = ((start + (end-start))/2); //also pivot value
double max = 1;
if(array[middle] > array[start])
max = 2;
if(array[end] > array[start] && array[end] > array[middle])
max = 3;
double min = 1;
if(array[middle] < array[start])
min = 2;
if(array[end] < array[start] && array[end]< array[middle])
min = 3;
if(min*max == 2)
pivot = end;
else if(min*max == 3)
pivot = (start+end)/2;
else if(min*max == 6)
pivot = start;
else
pivot = 1;
return pivot;
}
// Quicksort driver
public void Quicksort(double[] array){
// Check for empty or null array
if (array ==null || array.length==0){
return;
}
double number = array.length;
Quicksort(array, 0, (int) (number - 1));
}
public void Quicksort(double []array, int start, int end)
{
int i = start;
int j = end;
int pivot_index = getPivot(array, start, end);
double pivot_val = array[pivot_index];
while(i <= j)
{
while(array[i] < pivot_val)
{
i++;
}
while(array[j] > pivot_val)
{
j--;
}
if( i <= j)
{
swap(array,i,j);
i++;
j--;
}
}
if(start < j)
Quicksort(array,start,j);
if(i < end)
Quicksort(array,i,end-1);
}
Point[] pointer = new Point[18];
public void createPoints()
{
pointer[0] = new Point(1,1);
pointer[1] = new Point(1,2);
pointer[2] = new Point(1,3);
pointer[3] = new Point(1,4);
pointer[4] = new Point(1,5);
pointer[5] = new Point(1,6);
pointer[6] = new Point(2,1);
pointer[7] = new Point(2,4);
pointer[8] = new Point(3,2);
pointer[9] = new Point(3,3);
pointer[10] = new Point(4,2);
pointer[11] = new Point(4,3);
pointer[12] = new Point(4,4);
pointer[13] = new Point(4,5);
pointer[14] = new Point(5,1);
pointer[15] = new Point(5,4);
pointer[16] = new Point(6,4);
pointer[17] = new Point(4,1);
}
int collinear=0;// declare colinercount to 0
public void findSlope()
{
double[] slope; // declare slope array
slope = new double[pointer.length-1]; //size as the amount of points
for(int i = 0; i < pointer.length-1; i++) // start with one selected point
{
int k = 0; // index for the slope array
// for point i, find all points (omit i by i+1)
for(int j = i+1; j < pointer.length-1; j++)
{
if(pointer[j].getX()-pointer[i].getX() != 0) // checks if the dominator is zero to prevent division by zero
{
// for point i, find all slope
slope[k] = (( pointer[j].getY()-pointer[i].getY() ) / ( pointer[j].getX()-pointer[i].getX() )); // calculate slope a from ax+b
k++;
}
}
Quicksort(slope, 0, slope.length-1-i); // sort the array
for(int j = 0; j < slope.length-3-i; j++) // the reason for -3: We are gonna look through the array 3 index in. to prevent ArrayOutOfBound.
{
//find the same slope value for 4 points
if(slope[j]==slope[j+1] && slope[j+1] == slope[j+2] && slope[j+2] == slope[j+3])
{
//if condition is true, then add to collinear count.
collinear++;
}
}
}
}
public void running()
{
createPoints();
findSlope();
}
public void printout()
{
System.out.print("Points in the plane:\n");
for(int i = 0 ; i < pointer.length; i++)
System.out.print("(" + pointer[i].getX() + ", " + pointer[i].getY() + ")\n");
System.out.print("Collinear: " + collinear + "\n");
}
public static void main( String [ ] args )
{
colinear test = new colinear();
test.running();
test.printout();
}
}