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Btree Implementation
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| /** | |
| * Copyright 2017 Ambud Sharma | |
| * | |
| * Licensed under the Apache License, Version 2.0 (the "License"); | |
| * you may not use this file except in compliance with the License. | |
| * You may obtain a copy of the License at | |
| * | |
| * http://www.apache.org/licenses/LICENSE-2.0 | |
| * | |
| * Unless required by applicable law or agreed to in writing, software | |
| * distributed under the License is distributed on an "AS IS" BASIS, | |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
| * See the License for the specific language governing permissions and | |
| * limitations under the License. | |
| */ | |
| package btree.btree; | |
| import java.util.Arrays; | |
| /** | |
| * Btree Implementation | |
| */ | |
| @SuppressWarnings("unused") | |
| public class Btree { | |
| private Node root; | |
| public void insert(int key) { | |
| Node insert = insert(key, root); | |
| if (insert != null) { | |
| root = insert; | |
| } | |
| } | |
| public Node insert(int key, Node node) { | |
| int i = 0; | |
| for (; i < node.count; i++) { | |
| if (key < node.keys[i]) { | |
| break; | |
| } | |
| } | |
| if (node.isLeaf) { | |
| for (int k = node.keys.length - 1; k > i; k--) { | |
| node.keys[k] = node.keys[k - 1]; | |
| } | |
| node.count++; | |
| node.keys[i] = key; | |
| } else { | |
| Node node2 = node.children[i]; | |
| if (node2 == null) { | |
| node2 = new Node(); | |
| } | |
| Node insert = insert(key, node2); | |
| if (insert != null) { | |
| for (int k = node.keys.length - 1; k > i; k--) { | |
| node.keys[k] = node.keys[k - 1]; | |
| node.children[k + 1] = node.children[k]; | |
| } | |
| node.count++; | |
| node.keys[i] = insert.keys[0]; | |
| node.children[i] = insert.children[0]; | |
| node.children[i + 1] = insert.children[1]; | |
| } | |
| } | |
| if (node.count == node.keys.length) { | |
| return split(node); | |
| } | |
| return null; | |
| } | |
| public static Node split(Node node) { | |
| int splitpoint = node.count / 2; | |
| int splitKey = node.keys[splitpoint]; | |
| Node nn = new Node(); | |
| for (int i = splitpoint + 1, j = 0; i < node.keys.length; i++, j++) { | |
| nn.keys[j] = node.keys[i]; | |
| node.keys[i] = 0; | |
| } | |
| node.keys[splitpoint] = 0; | |
| if (!node.isLeaf) { | |
| nn.isLeaf = false; | |
| for (int i = splitpoint + 1, j = 0; i < node.children.length; i++, j++) { | |
| nn.children[j] = node.children[i]; | |
| node.children[i] = null; | |
| } | |
| } else { | |
| nn.isLeaf = true; | |
| } | |
| nn.count = splitpoint; | |
| node.count = splitpoint; | |
| Node parent = new Node(); | |
| parent.isLeaf = false; | |
| parent.keys[0] = splitKey; | |
| parent.count++; | |
| parent.children[0] = node; | |
| parent.children[1] = nn; | |
| return parent; | |
| } | |
| public boolean findNode(int key) { | |
| Node result = findNode(key, root); | |
| return result != null; | |
| } | |
| public Node findNode(int key, Node node) { | |
| if (node.isLeaf) { | |
| for (int i = 0; i < node.count; i++) { | |
| if (node.keys[i] == key) { | |
| return node; | |
| } | |
| } | |
| return null; | |
| } else { | |
| int i = 0; | |
| for (; i < node.count; i++) { | |
| if (key < node.keys[i]) { | |
| break; | |
| } else if (key == node.keys[i]) { | |
| return node; | |
| } | |
| } | |
| return findNode(key, node.children[i]); | |
| } | |
| } | |
| public static void main(String[] args) { | |
| testInserts(); | |
| // testSearch(); | |
| // testSplits(); | |
| } | |
| private static void testInserts() { | |
| Btree tree = new Btree(); | |
| tree.root = new Node(); | |
| tree.root.isLeaf = true; | |
| tree.insert(5); | |
| tree.insert(2); | |
| tree.insert(4); | |
| tree.insert(10); | |
| tree.insert(1); | |
| tree.insert(11); | |
| tree.insert(15); | |
| tree.insert(7); | |
| tree.insert(9); | |
| tree.insert(12); | |
| tree.insert(3); | |
| tree.insert(8); | |
| System.out.println("\nRoot:" + tree.root); | |
| System.out.println("\nRoot keys:" + Arrays.toString(tree.root.keys)); | |
| for (int i = 0; i < 20; i++) { | |
| System.out.println(tree.findNode(i) + "\t" + i); | |
| } | |
| } | |
| private static void testSplits() { | |
| Node node = new Node(); | |
| node.isLeaf = false; | |
| node.keys[0] = 4; | |
| node.keys[1] = 8; | |
| node.keys[2] = 13; | |
| node.count = 3; | |
| node.children[0] = new Node(); | |
| node.children[0].isLeaf = true; | |
| node.children[0].keys[0] = 0; | |
| node.children[0].keys[1] = 1; | |
| node.children[0].keys[2] = 2; | |
| node.children[0].count = 3; | |
| node.children[1] = new Node(); | |
| node.children[1].isLeaf = true; | |
| node.children[1].keys[0] = 5; | |
| node.children[1].keys[1] = 6; | |
| node.children[1].keys[2] = 7; | |
| node.children[1].count = 3; | |
| node.children[2] = new Node(); | |
| node.children[2].isLeaf = true; | |
| node.children[2].keys[0] = 10; | |
| node.children[2].keys[1] = 11; | |
| node.children[2].keys[2] = 12; | |
| node.children[2].count = 3; | |
| node.children[3] = new Node(); | |
| node.children[3].isLeaf = true; | |
| node.children[3].keys[0] = 15; | |
| node.children[3].keys[1] = 16; | |
| node.children[3].keys[2] = 17; | |
| node.children[3].count = 3; | |
| Node split = split(node); | |
| System.out.println(split); | |
| split = new Node(); | |
| split.isLeaf = true; | |
| split.keys[0] = 15; | |
| split.keys[1] = 16; | |
| split.keys[2] = 17; | |
| split.count = 3; | |
| System.out.println(split(split)); | |
| } | |
| public static void testSearch() { | |
| Btree tree = new Btree(); | |
| tree.root = new Node(); | |
| tree.root.keys[0] = 3; | |
| tree.root.keys[1] = 6; | |
| tree.root.count = 2; | |
| tree.root.children[0] = new Node(); | |
| tree.root.children[0].isLeaf = true; | |
| tree.root.children[0].count = 3; | |
| tree.root.children[0].keys[0] = 0; | |
| tree.root.children[0].keys[1] = 1; | |
| tree.root.children[0].keys[2] = 2; | |
| tree.root.children[1] = new Node(); | |
| tree.root.children[1].isLeaf = true; | |
| tree.root.children[1].count = 2; | |
| tree.root.children[1].keys[0] = 4; | |
| tree.root.children[1].keys[1] = 5; | |
| tree.root.children[2] = new Node(); | |
| tree.root.children[2].isLeaf = true; | |
| tree.root.children[2].count = 2; | |
| tree.root.children[2].keys[0] = 7; | |
| tree.root.children[2].keys[1] = 9; | |
| System.out.println("1:" + tree.findNode(1, tree.root)); | |
| System.out.println("3:" + tree.findNode(3, tree.root)); | |
| System.out.println("5:" + tree.findNode(5, tree.root)); | |
| System.out.println("8:" + tree.findNode(8, tree.root)); | |
| System.out.println("9:" + tree.findNode(9, tree.root)); | |
| } | |
| public static class Node { | |
| static final int MAX = 8; | |
| int count; | |
| int[] keys = new int[MAX - 1]; | |
| boolean isLeaf; | |
| Node[] children = new Node[MAX]; | |
| /* | |
| * (non-Javadoc) | |
| * | |
| * @see java.lang.Object#toString() | |
| */ | |
| @Override | |
| public String toString() { | |
| return "\nNode [count=" + count + ", keys=" + Arrays.toString(keys) + ", isLeaf=" + isLeaf + "" | |
| + ((!isLeaf) ? ", children=" + Arrays.toString(children) : "") + "]"; | |
| } | |
| } | |
| } |
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