CODEWITHSUNDEEP
javadistance
Darron Martinez
Darron Martinez

Reputation: 49

Finding the closest point

In my program, I am attempting to find the closest point from the starting position (0,0), then "move" again to the next point. The points are read in through a file. The next point I am trying to move to is the "closest" point. I use the Pythagorean Theorem to find the distance. But what can I do to "check" the point I am going to to determine if I have already have visited it. For instance, if the point is 0,0, and then it goes to 1,1, how do check to "tell" the program that 0,0 is no longer an option?

public class PointsNStuff {
    public static void main(String [] args) {

        final int P = StdIn.readInt();
        double [] x = new double[P];
        double [] y = new double[P];
        double [] visit= new double[P]; //Set an array that stores points that have been visited already
        double [] math= new double[P]; //Set an array that stores the distance to all the points


        for( int i= 0; i< P; i++){ //Store the values from the text file
            x[i] = StdIn.readDouble();
            y[i] = StdIn.readDouble();
        }

        double lowX = x[0];

        double lowY = y[0];

        double highX = x[0];

        double highY = y[0];

        //Find the lowest X and the lowest Y values:

        for (int i = 0; i < P; i++){
            if (lowX > x[i])
                lowX = x[i];
        }for (int i = 0; i < P; i++){
            if (lowY > y[i])
                lowY = y[i];
        }
        for (int i = 0; i < P; i++){
            if (highX < x[i])
                highX = x[i];
        }
        for (int i = 0; i < P; i++){
            if (highY < y[i])
                highY = y[i];
        }
        System.out.println(lowX + " " + lowY);
        System.out.println(highX + " " + highY);
        System.out.println("");
        System.out.println(P);

        //Determine the closest point
        double xCoord=0.0;
        double yCoord=0.0;
        double dist = -1.0;
        for (int i= 0; i < P; i ++){ //Repeat entire section for all P (number of points)
            for (int j = 0; j < P; j++){ //Find the distance between current point and all other points. Go through all points (do the math).
                xCoord = x[j]; // # x point
                yCoord = y[j]; // # y point
                double save= Math.sqrt( ( (xCoord+x[j]) * (xCoord+x[j]) ) + ( (yCoord + y[j]) * (yCoord + y[j]) ) ); //Pythagorean theorem
                save = math[j]; //store the distance in the array slot
            }
            for (int j = 0; j < P; j++){
                if (dist < math[j]){
                    dist = math[j];

                    //What boolean check can I put here to double check whether I have visited this point already?

                    xCoord = x[j]; // set the two points to what number they should be at.
                    yCoord = y[j];
                }
            }
            System.out.println(xCoord + " " + yCoord);
        }
    }
}

I have not used any points into the Array I named "visit". Any and all help is appreciated! Thanks!

Upvotes: 0

Views: 1439

Answers (2)

snvrthn
snvrthn

Reputation: 385

Use ArrayList to Store points,

ArrayList<Double> x = new ArrayList<Double>();
ArrayList<Double> y = new ArrayList<Double>();

add points to arraylist,

for( int i= 0; i< P; i++){ //Store the values from the text file
  x.add(StdIn.readDouble());
  y.add(StdIn.readDouble());
}

select point from araylist,

x.get(i); insted of x[i];
y.get(i); insted of y[i];

and remove already used points,

x.remove(new Double(used_x_value));
y.remove(new Double(used_y_value));

see Class ArrayList

Upvotes: 1

md_rasler
md_rasler

Reputation: 386

What you have here is a perfect candidate for encapsulation! I would start by thinking about another object to encapsulate the 'point' concept you keep referring to:

class Point {
    private final double x;
    private final double y;

    public Point(double x, double y) {
        this.x = x;
        this.y = y;
    }

    public double getX() {
        return x;
    }

    public double getY() {
        return y;
    }
}

One minor caveat: this assumes that you will not have duplicate x,y pairs in the input file. If you do, you may need to override hashcode and equals. But if not, this should do it. Then you can put these Points into a data structure ( see HashSet ) like this:

import java.util.Set; import java.util.HashSet;

public class PointsNStuff {

    public static void main(String args[]) {

        Set<Point> pointsVisited = new HashSet<>();

        //when you visit a point, put it in the set like this
        //the numbers are just for example
        Point currentPoint = new Point(10.0, 12.0);
        pointsVisited.add(currentPoint);

        //now in the future you can check if you 'visited' this point
        if(!pointsVisited.contains(currentPoint)) {
            System.out.println("Haven't been to current point yet...");
        }

    }

}

Upvotes: 1

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