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BTree.java
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package com.interview.tree;
/**
* http://www.geeksforgeeks.org/b-tree-set-1-insert-2/
* http://www.geeksforgeeks.org/b-tree-set-1-introduction-2/
*/
public class BTree {
private BTreeNode root = null;
private static int T = 2;
public void insert(int data){
if(root == null){
root = BTreeNode.newNode(data);
return;
}
SplitResult sr = insert(root,data);
if(sr != null){
BTreeNode newRoot = BTreeNode.newNode();
newRoot.n = 1;
newRoot.isLeaf = false;
newRoot.keys[0] = sr.c;
newRoot.child[0] = sr.r1;
newRoot.child[1] = sr.r2;
root = newRoot;
}
}
public boolean search(int data){
return search(root,data);
}
public boolean search(BTreeNode root, int data){
int i =0;
while(i < root.n && root.keys[i] < data){
i++;
}
if(i < root.n && root.keys[i] == data){
return true;
}
if(root.isLeaf){
return false;
}
return search(root.child[i],data);
}
private SplitResult insert(BTreeNode root,int data){
if(root.isLeaf){
if(!root.isFull()){
root.insertKey(data, null, null);
return null;
}else{
SplitResult sr = splitNode(root,data,null,null);
return sr;
}
}else{
int i=0;
for(; i < root.n; i++){
if(data <= root.keys[i]){
SplitResult sr = insert(root.child[i],data);
if(sr == null){
return null;
}else{
if(!root.isFull()){
root.insertKey(sr.c, sr.r1, sr.r2);
return null;
}else{
SplitResult sr1 = splitNode(root,sr.c,sr.r1,sr.r2);
return sr1;
}
}
}
}
if(i == root.n){
SplitResult sr = insert(root.child[i],data);
if(sr == null){
return null;
}else{
if(!root.isFull()){
root.insertKey(sr.c, sr.r1, sr.r2);
return null;
}else{
SplitResult sr1 = splitNode(root,sr.c,sr.r1,sr.r2);
return sr1;
}
}
}
}
return null;
}
private SplitResult splitNode(BTreeNode node,int data, BTreeNode nr1, BTreeNode nr2){
int c = node.keys[node.n/2];
BTreeNode r1 = BTreeNode.newNode();
BTreeNode r2 = BTreeNode.newNode();
r1.n = node.n/2;
r2.n = node.n - node.n/2-1;
if(!node.isLeaf){
r1.isLeaf = false;
r2.isLeaf = false;
}
int i=0;
for(; i < node.n/2; i++){
r1.keys[i] = node.keys[i];
r1.child[i] = node.child[i];
}
r1.child[i] = node.child[i];
i = node.n/2 + 1;
int j=0;
for(;i < node.n; i++,j++){
r2.keys[j] = node.keys[i];
r2.child[j] = node.child[i];
}
r2.child[j] = node.child[i];
if(data < c){
r1.insertKey(data, nr1, nr2);
}else{
r2.insertKey(data, nr1, nr2);
}
SplitResult sr = new SplitResult();
sr.c = c;
sr.r1 = r1;
sr.r2 = r2;
return sr;
}
class SplitResult{
BTreeNode r1;
BTreeNode r2;
int c;
}
public void traverse(){
traverse(root);
}
private void traverse(BTreeNode root){
for(int i=0; i < root.n; i++){
if(!root.isLeaf){
traverse(root.child[i]);
}
System.out.print(root.keys[i] + " ");
}
if(!root.isLeaf){
traverse(root.child[root.n]);
}
}
static class BTreeNode{
int n ;
BTreeNode[] child = new BTreeNode[2*T];
int keys[] = new int[2*T-1];
boolean isLeaf;
public void insertKey(int data,BTreeNode r1,BTreeNode r2){
int i = n-1;
while(i >=0 && data < keys[i]){
keys[i+1] = keys[i];
i--;
}
keys[i+1] = data;
int j = n;
while(j > i+1){
child[j+1] = child[j];
j--;
}
child[j] = r1;
child[j+1] = r2;
n++;
}
public static BTreeNode newNode(int data){
BTreeNode node = new BTreeNode();
node.keys[0] = data;
node.isLeaf = true;
node.n = 1;
return node;
}
public static BTreeNode newNode(){
BTreeNode node = new BTreeNode();
node.isLeaf = true;
node.n = 0;
return node;
}
public boolean isFull(){
return 2*T - 1 == n;
}
}
public static void main(String args[]){
BTree bTree = new BTree();
bTree.insert(5);
bTree.insert(4);
bTree.insert(3);
bTree.insert(2);
bTree.insert(1);
bTree.insert(6);
bTree.insert(11);
bTree.insert(13);
bTree.insert(8);
bTree.insert(7);
bTree.insert(10);
bTree.insert(9);
bTree.insert(28);
bTree.insert(22);
bTree.insert(12);
bTree.insert(18);
bTree.insert(16);
bTree.traverse();
System.out.print(bTree.search(28));
System.out.print(bTree.search(11));
System.out.print(bTree.search(5));
System.out.print(bTree.search(21));
System.out.print(bTree.search(3));
System.out.print(bTree.search(4));
System.out.print(bTree.search(14));
}
}