This is a Java Program to implement 2D KD Tree and print the various traversals. In computer science, a k-d tree (short for k-dimensional tree) is a space-partitioning data structure for organizing points in a k-dimensional space. k-d trees are a useful data structure for several applications, such as searches involving a multidimensional search key (e.g. range searches and nearest neighbor searches). k-d trees are a special case of binary space partitioning trees.
Here is the source code of the Java Program to Construct K-D Tree for 2 Dimensional Data (assume static data). The Java program is successfully compiled and run on a Windows system. The program output is also shown below.
//This is a java program to construct a KD tree for two dimensional static data import java.io.IOException; class KD2DNode { int axis; double[] x; int id; boolean checked; boolean orientation; KD2DNode Parent; KD2DNode Left; KD2DNode Right; public KD2DNode(double[] x0, int axis0) { x = new double[2]; axis = axis0; for (int k = 0; k < 2; k++) x[k] = x0[k]; Left = Right = Parent = null; checked = false; id = 0; } public KD2DNode FindParent(double[] x0) { KD2DNode parent = null; KD2DNode next = this; int split; while (next != null) { split = next.axis; parent = next; if (x0[split] > next.x[split]) next = next.Right; else next = next.Left; } return parent; } public KD2DNode Insert(double[] p) { x = new double[2]; KD2DNode parent = FindParent(p); if (equal(p, parent.x, 2) == true) return null; KD2DNode newNode = new KD2DNode(p, parent.axis + 1 < 2 ? parent.axis + 1 : 0); newNode.Parent = parent; if (p[parent.axis] > parent.x[parent.axis]) { parent.Right = newNode; newNode.orientation = true; // } else { parent.Left = newNode; newNode.orientation = false; // } return newNode; } boolean equal(double[] x1, double[] x2, int dim) { for (int k = 0; k < dim; k++) { if (x1[k] != x2[k]) return false; } return true; } double distance2(double[] x1, double[] x2, int dim) { double S = 0; for (int k = 0; k < dim; k++) S += (x1[k] - x2[k]) * (x1[k] - x2[k]); return S; } } class KD2DTree { KD2DNode Root; int TimeStart, TimeFinish; int CounterFreq; double d_min; KD2DNode nearest_neighbour; int KD_id; int nList; KD2DNode CheckedNodes[]; int checked_nodes; KD2DNode List[]; double x_min[], x_max[]; boolean max_boundary[], min_boundary[]; int n_boundary; public KD2DTree(int i) { Root = null; KD_id = 1; nList = 0; List = new KD2DNode[i]; CheckedNodes = new KD2DNode[i]; max_boundary = new boolean[2]; min_boundary = new boolean[2]; x_min = new double[2]; x_max = new double[2]; } public boolean add(double[] x) { if (nList >= 2000000 - 1) return false; // can't add more points if (Root == null) { Root = new KD2DNode(x, 0); Root.id = KD_id++; List[nList++] = Root; } else { KD2DNode pNode; if ((pNode = Root.Insert(x)) != null) { pNode.id = KD_id++; List[nList++] = pNode; } } return true; } public KD2DNode find_nearest(double[] x) { if (Root == null) return null; checked_nodes = 0; KD2DNode parent = Root.FindParent(x); nearest_neighbour = parent; d_min = Root.distance2(x, parent.x, 2); ; if (parent.equal(x, parent.x, 2) == true) return nearest_neighbour; search_parent(parent, x); uncheck(); return nearest_neighbour; } public void check_subtree(KD2DNode node, double[] x) { if ((node == null) || node.checked) return; CheckedNodes[checked_nodes++] = node; node.checked = true; set_bounding_cube(node, x); int dim = node.axis; double d = node.x[dim] - x[dim]; if (d * d > d_min) { if (node.x[dim] > x[dim]) check_subtree(node.Left, x); else check_subtree(node.Right, x); } else { check_subtree(node.Left, x); check_subtree(node.Right, x); } } public void set_bounding_cube(KD2DNode node, double[] x) { if (node == null) return; int d = 0; double dx; for (int k = 0; k < 2; k++) { dx = node.x[k] - x[k]; if (dx > 0) { dx *= dx; if (!max_boundary[k]) { if (dx > x_max[k]) x_max[k] = dx; if (x_max[k] > d_min) { max_boundary[k] = true; n_boundary++; } } } else { dx *= dx; if (!min_boundary[k]) { if (dx > x_min[k]) x_min[k] = dx; if (x_min[k] > d_min) { min_boundary[k] = true; n_boundary++; } } } d += dx; if (d > d_min) return; } if (d < d_min) { d_min = d; nearest_neighbour = node; } } public KD2DNode search_parent(KD2DNode parent, double[] x) { for (int k = 0; k < 2; k++) { x_min[k] = x_max[k] = 0; max_boundary[k] = min_boundary[k] = false; // } n_boundary = 0; KD2DNode search_root = parent; while (parent != null && (n_boundary != 2 * 2)) { check_subtree(parent, x); search_root = parent; parent = parent.Parent; } return search_root; } public void uncheck() { for (int n = 0; n < checked_nodes; n++) CheckedNodes[n].checked = false; } public void inorder() { inorder(Root); } private void inorder(KD2DNode root) { if (root != null) { inorder(root.Left); System.out.print("(" + root.x[0] + ", " + root.x[1] + ") "); inorder(root.Right); } } public void preorder() { preorder(Root); } private void preorder(KD2DNode root) { if (root != null) { System.out.print("(" + root.x[0] + ", " + root.x[1] + ") "); inorder(root.Left); inorder(root.Right); } } public void postorder() { postorder(Root); } private void postorder(KD2DNode root) { if (root != null) { inorder(root.Left); inorder(root.Right); System.out.print("(" + root.x[0] + ", " + root.x[1] + ") "); } } } public class KDTree_TwoD_Data { public static void main(String args[]) throws IOException { int numpoints = 5; KD2DTree kdt = new KD2DTree(numpoints); double x[] = new double[2]; x[0] = 0.0; x[1] = 0.0; kdt.add(x); x[0] = 3.3; x[1] = 1.5; kdt.add(x); x[0] = 4.7; x[1] = 11.1; kdt.add(x); x[0] = 5.0; x[1] = 12.3; kdt.add(x); x[0] = 5.1; x[1] = 1.2; kdt.add(x); System.out.println("Inorder of 2D Kd tree: "); kdt.inorder(); System.out.println("\nPreorder of 2D Kd tree: "); kdt.preorder(); System.out.println("\nPostorder of 2D Kd tree: "); kdt.postorder(); } }
Output:
$ javac KDTree_TwoD_Data.java $ java KDTree_TwoD_Data Inorder of 2D Kd tree: (0.0, 0.0) (5.1, 1.2) (3.3, 1.5) (4.7, 11.1) (5.0, 12.3) Preorder of 2D Kd tree: (0.0, 0.0) (5.1, 1.2) (3.3, 1.5) (4.7, 11.1) (5.0, 12.3) Postorder of 2D Kd tree: (5.1, 1.2) (3.3, 1.5) (4.7, 11.1) (5.0, 12.3) (0.0, 0.0)
Related posts:
Tìm hiểu về xác thực và phân quyền trong ứng dụng
Using JWT with Spring Security OAuth
Java Program to Implement Find all Cross Edges in a Graph
Java Program to Implement HashTable API
Java Program to Implement K Way Merge Algorithm
Java Program to Implement Vector API
Spring Data – CrudRepository save() Method
Java Program to Emulate N Dice Roller
Java Program to Implement the Alexander Bogomolny’s UnOrdered Permutation Algorithm for Elements Fro...
Hướng dẫn Java Design Pattern – Command
Spring Security with Maven
Custom JUnit 4 Test Runners
File Upload with Spring MVC
Java Program to Implement Skip List
Guide to Escaping Characters in Java RegExps
The Basics of Java Security
Spring Security Remember Me
Spring Cloud AWS – S3
Compact Strings in Java 9
An Intro to Spring Cloud Vault
Prevent Brute Force Authentication Attempts with Spring Security
Java Program to Solve Tower of Hanoi Problem using Stacks
Guide to java.util.concurrent.BlockingQueue
Java Program to Find the Number of Ways to Write a Number as the Sum of Numbers Smaller than Itself
Java Program to Implement CopyOnWriteArrayList API
Java Program to Check Whether Graph is DAG
Java Program to Implement Stack using Linked List
Tìm hiểu về Web Service
How to Find an Element in a List with Java
A Guide to the Java LinkedList
Spring Boot - Database Handling
Java Program to Perform Left Rotation on a Binary Search Tree