Can you guys look at my code and let me know how to improve it? I'm finding the closed set of points (X,Y) in 2D plane. I need to do it in O(n^2) and O(nlogn). O(n^2) was easy. My problems are on the Divide and Conquer approach. I've been up two days trying to do it, but I can't seem to get it right. I couldn't check my method completely because I got a null pointer exception when I sorted my array by the X-coordinate. I'm sure I'll have more errors. Also I'm not sure if this was the correct approach, I followed this: http://www.cs.mcgill.ca/~cs251/ClosestPair/ClosestPairDQ.html

Also how do I keep track of which points are the closest ones..... my method only return the distance between the closest points

double dL; double dR; double d; double stVal = Double.POSITIVE_INFINITY; public double closestPoints(int l, int r) { if((r - l) ==2){ stVal=array[0].eucDist(array[1]); //eucDist computes distance between two points return stVal; } if((r-l)<2){ stVal=stVal-1; return stVal; } int median = (r-l)/2; dL = closestPoints(l, median); dR = closestPoints(median+1, r); double d; if(dL<=dR) d=dL; else d=dR; Point[] Y; int n = 0;//next two for loops compute the number of Points with X < = than d for(int i = median; Math.abs(array[i].getX())<=d; i--){ n++; } for(int i=median+1; Math.abs(array[i].getX())<=d; i++){ n++; } Y = new Point[n]; int index = 0;//next two for loops fill Y with points that have X value < = than d for(int i = median; Math.abs(array[i].getX())<=d; i--){ Y[index]=array[i]; index++; } for(int i=median+1; Math.abs(array[i].getX())<=d; i++){ Y[index]=array[i]; index++; } Arrays.sort(Y, new Point.CompY()); //sort Y by increasing Y coordinate double dY = Double.POSITIVE_INFINITY; for(int i=0; i<=array.length-2; i++) { for(int j=i+1; j<=array.length-1; j++) {//xx, yy initialized alreay doubles xx = Math.pow((array[i].getX()-array[j].getX()), 2); yy = Math.pow((array[i].getY()-array[j].getY()), 2); dY = Math.sqrt(xx+yy); if(dY < d) { d = dY; } } } return d; }----------------------------------------------------------- public static void main(String[] args) { MyClass class = new MyClass("Points.txt"); Arrays.sort(driver.array, new Point.CompX()); MyClass.closestPoints(0, MyClass.array.length);

OK I figured that I wasn't filling the array with the values. Sorry I was tired last night. This is what I get:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1
at project.myClass.closestPoints(myClass.java:140)
at project.myClass.closestPoints(myClass.java:131)
at project.myClass.closestPoints(myClass.java:131)
at project.myClass.closestPoints(myClass.java:131)
at project.myClass.closestPoints(myClass.java:131)
at project.myClass.closestPoints(myClass.java:131)
at project.myClass.closestPoints(myClass.java:131)
at project.myClass.closestPoints(myClass.java:131)
at project.myClass.closestPoints(myClass.java:131)
at project.myClass.closestPoints(myClass.java:131)
at project.FindPoints.main(closestPoints.java:14)

where line 131:
dL = closestPoints(l, median);
line 140:
dR = fcp(median+1, r);

line 14 on main class
myClass.closestPoints(0, myClass.array.length);

Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…

Introduction
This article is the first of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article explains our test automation goals. Then rationale is given for the tools we use to a…

Viewers will learn one way to get user input in Java.
Introduce the Scanner object:
Declare the variable that stores the user input:
An example prompting the user for input:
Methods you need to invoke in order to properly get user input:

Viewers will learn about the regular for loop in Java and how to use it.
Definition:
Break the for loop down into 3 parts:
Syntax when using for loops:
Example using a for loop: