java b+樹的實現
阿新 • • 發佈:2018-12-23
B+樹的定義:
1.任意非葉子結點最多有M個子節點;且M>2;
2.除根結點以外的非葉子結點至少有 M/2個子節點;
3.根結點至少有2個子節點;
4.除根節點外每個結點存放至少M/2和至多M個關鍵字;(至少2個關鍵字)
5.非葉子結點的子樹指標與關鍵字個數相同;
6.所有結點的關鍵字:K[1], K[2], …, K[M];且K[i] < K[i+1];
7.非葉子結點的子樹指標P[i],指向關鍵字值屬於[K[i], K[i+1])的子樹;
8.所有葉子結點位於同一層;
5.為所有葉子結點增加一個鏈指標;
6.所有關鍵字都在葉子結點出現;
Java實現: 介面: Java程式碼- package com.meidusa.test;
- publicinterface B {
- public Object get(Comparable key); //查詢
- publicvoid remove(Comparable key); //移除
- publicvoid insertOrUpdate(Comparable key, Object obj); //插入或者更新,如果已經存在,就更新,否則插入
- }
B+樹: Java程式碼package com.meidusa.test; public interface B { public Object get(Comparable key); //查詢 public void remove(Comparable key); //移除 public void insertOrUpdate(Comparable key, Object obj); //插入或者更新,如果已經存在,就更新,否則插入 }
- package com.meidusa.test;
- import java.util.Random;
- publicclass BplusTree implements B {
- /** 根節點 */
- protected Node root;
- /** 階數,M值 */
- protectedint order;
- /** 葉子節點的連結串列頭*/
- protected Node head;
- public Node getHead() {
- return head;
- }
- public
- this.head = head;
- }
- public Node getRoot() {
- return root;
- }
- publicvoid setRoot(Node root) {
- this.root = root;
- }
- publicint getOrder() {
- return order;
- }
- publicvoid setOrder(int order) {
- this.order = order;
- }
- @Override
- public Object get(Comparable key) {
- return root.get(key);
- }
- @Override
- publicvoid remove(Comparable key) {
- root.remove(key, this);
- }
- @Override
- publicvoid insertOrUpdate(Comparable key, Object obj) {
- root.insertOrUpdate(key, obj, this);
- }
- public BplusTree(int order){
- if (order < 3) {
- System.out.print("order must be greater than 2");
- System.exit(0);
- }
- this.order = order;
- root = new Node(true, true);
- head = root;
- }
- //測試
- publicstaticvoid main(String[] args) {
- BplusTree tree = new BplusTree(6);
- Random random = new Random();
- long current = System.currentTimeMillis();
- for (int j = 0; j < 100000; j++) {
- for (int i = 0; i < 100; i++) {
- int randomNumber = random.nextInt(1000);
- tree.insertOrUpdate(randomNumber, randomNumber);
- }
- for (int i = 0; i < 100; i++) {
- int randomNumber = random.nextInt(1000);
- tree.remove(randomNumber);
- }
- }
- long duration = System.currentTimeMillis() - current;
- System.out.println("time elpsed for duration: " + duration);
- int search = 80;
- System.out.print(tree.get(search));
- }
- }
package com.meidusa.test;
import java.util.Random;
public class BplusTree implements B {
/** 根節點 */
protected Node root;
/** 階數,M值 */
protected int order;
/** 葉子節點的連結串列頭*/
protected Node head;
public Node getHead() {
return head;
}
public void setHead(Node head) {
this.head = head;
}
public Node getRoot() {
return root;
}
public void setRoot(Node root) {
this.root = root;
}
public int getOrder() {
return order;
}
public void setOrder(int order) {
this.order = order;
}
@Override
public Object get(Comparable key) {
return root.get(key);
}
@Override
public void remove(Comparable key) {
root.remove(key, this);
}
@Override
public void insertOrUpdate(Comparable key, Object obj) {
root.insertOrUpdate(key, obj, this);
}
public BplusTree(int order){
if (order < 3) {
System.out.print("order must be greater than 2");
System.exit(0);
}
this.order = order;
root = new Node(true, true);
head = root;
}
//測試
public static void main(String[] args) {
BplusTree tree = new BplusTree(6);
Random random = new Random();
long current = System.currentTimeMillis();
for (int j = 0; j < 100000; j++) {
for (int i = 0; i < 100; i++) {
int randomNumber = random.nextInt(1000);
tree.insertOrUpdate(randomNumber, randomNumber);
}
for (int i = 0; i < 100; i++) {
int randomNumber = random.nextInt(1000);
tree.remove(randomNumber);
}
}
long duration = System.currentTimeMillis() - current;
System.out.println("time elpsed for duration: " + duration);
int search = 80;
System.out.print(tree.get(search));
}
}
節點:
Java程式碼
- package com.meidusa.test;
- import java.util.AbstractMap.SimpleEntry;
- import java.util.ArrayList;
- import java.util.List;
- import java.util.Map.Entry;
- publicclass Node {
- /** 是否為葉子節點 */
- protectedboolean isLeaf;
- /** 是否為根節點*/
- protectedboolean isRoot;
- /** 父節點 */
- protected Node parent;
- /** 葉節點的前節點*/
- protected Node previous;
- /** 葉節點的後節點*/
- protected Node next;
- /** 節點的關鍵字 */
- protected List<Entry<Comparable, Object>> entries;
- /** 子節點 */
- protected List<Node> children;
- public Node(boolean isLeaf) {
- this.isLeaf = isLeaf;
- entries = new ArrayList<Entry<Comparable, Object>>();
- if (!isLeaf) {
- children = new ArrayList<Node>();
- }
- }
- public Node(boolean isLeaf, boolean isRoot) {
- this(isLeaf);
- this.isRoot = isRoot;
- }
- public Object get(Comparable key) {
- //如果是葉子節點
- if (isLeaf) {
- for (Entry<Comparable, Object> entry : entries) {
- if (entry.getKey().compareTo(key) == 0) {
- //返回找到的物件
- return entry.getValue();
- }
- }
- //未找到所要查詢的物件
- returnnull;
- //如果不是葉子節點
- }else {
- //如果key小於等於節點最左邊的key,沿第一個子節點繼續搜尋
- if (key.compareTo(entries.get(0).getKey()) <= 0) {
- return children.get(0).get(key);
- //如果key大於節點最右邊的key,沿最後一個子節點繼續搜尋
- }elseif (key.compareTo(entries.get(entries.size()-1).getKey()) >= 0) {
- return children.get(children.size()-1).get(key);
- //否則沿比key大的前一個子節點繼續搜尋
- }else {
- for (int i = 0; i < entries.size(); i++) {
- if (entries.get(i).getKey().compareTo(key) <= 0 && entries.get(i+1).getKey().compareTo(key) > 0) {
- return children.get(i).get(key);
- }
- }
- }
- }
- returnnull;
- }
- publicvoid insertOrUpdate(Comparable key, Object obj, BplusTree tree){
- //如果是葉子節點
- if (isLeaf){
- //不需要分裂,直接插入或更新
- if (contains(key) || entries.size() < tree.getOrder()){
- insertOrUpdate(key, obj);
- if (parent != null) {
- //更新父節點
- parent.updateInsert(tree);
- }
- //需要分裂
- }else {
- //分裂成左右兩個節點
- Node left = new Node(true);
- Node right = new Node(true);
- //設定連結
- if (previous != null){
- previous.setNext(left);
- left.setPrevious(previous);
- }
- if (next != null) {
- next.setPrevious(right);
- right.setNext(next);
- }
- if (previous == null){
- tree.setHead(left);
- }
- left.setNext(right);
- right.setPrevious(left);
- previous = null;
- next = null;
- //左右兩個節點關鍵字長度
- int leftSize = (tree.getOrder() + 1) / 2 + (tree.getOrder() + 1) % 2;
- int rightSize = (tree.getOrder() + 1) / 2;
- //複製原節點關鍵字到分裂出來的新節點
- insertOrUpdate(key, obj);
- for (int i = 0; i < leftSize; i++){
- left.getEntries().add(entries.get(i));
- }
- for (int i = 0; i < rightSize; i++){
- right.getEntries().add(entries.get(leftSize + i));
- }
- //如果不是根節點
- if (parent != null) {
- //調整父子節點關係
- int index = parent.getChildren().indexOf(this);
- parent.getChildren().remove(this);
- left.setParent(parent);
- right.setParent(parent);
- parent.getChildren().add(index,left);
- parent.getChildren().add(index + 1, right);
- setEntries(null);
- setChildren(null);
- //父節點插入或更新關鍵字
- parent.updateInsert(tree);
- setParent(null);
- //如果是根節點
- }else {
- isRoot = false;
- Node parent = new Node(false, true);
- tree.setRoot(parent);
- left.setParent(parent);
- right.setParent(parent);
- parent.getChildren().add(left);
- parent.getChildren().add(right);
- setEntries(null);
- setChildren(null);
- //更新根節點
- parent.updateInsert(tree);
- }
- }
- //如果不是葉子節點
- }else {
- //如果key小於等於節點最左邊的key,沿第一個子節點繼續搜尋
- if (key.compareTo(entries.get(0).getKey()) <= 0) {
- children.get(0).insertOrUpdate(key, obj, tree);
- //如果key大於節點最右邊的key,沿最後一個子節點繼續搜尋
- }elseif (key.compareTo(entries.get(entries.size()-1).getKey()) >= 0) {
- children.get(children.size()-1).insertOrUpdate(key, obj, tree);
- //否則沿比key大的前一個子節點繼續搜尋
- }else {
- for (int i = 0; i < entries.size(); i++) {
- if (entries.get(i).getKey().compareTo(key) <= 0 && entries.get(i+1).getKey().compareTo(key) > 0) {
- children.get(i).insertOrUpdate(key, obj, tree);
- break;
- }
- }
- }
- }
- }
- /** 插入節點後中間節點的更新 */
- protectedvoid updateInsert(BplusTree tree){
- validate(this, tree);
- //如果子節點數超出階數,則需要分裂該節點
- if (children.size() > tree.getOrder()) {
- //分裂成左右兩個節點
- Node left = new Node(false);
- Node right = new Node(false);
- //左右兩個節點關鍵字長度
- int leftSize = (tree.getOrder() + 1) / 2 + (tree.getOrder() + 1) % 2;
- int rightSize = (tree.getOrder() + 1) / 2;
- //複製子節點到分裂出來的新節點,並更新關鍵字
- for (int i = 0; i < leftSize; i++){
- left.getChildren().add(children.get(i));
- left.getEntries().add(new SimpleEntry(children.get(i).getEntries().get(0).getKey(), null));
- children.get(i).setParent(left);
- }
- for (int i = 0; i < rightSize; i++){
- right.getChildren().add(children.get(leftSize + i));
- right.getEntries().add(new SimpleEntry(children.get(leftSize + i).getEntries().get(0).getKey(), null));
- children.get(leftSize + i).setParent(right);
- }
- //如果不是根節點
- if (parent != null) {
- //調整父子節點關係
- int index = parent.getChildren().indexOf(this);
- parent.getChildren().remove(this);
- left.setParent(parent);
- right.setParent(parent);
- parent.getChildren().add(index,left);
- parent.getChildren().add(index + 1, right);
- setEntries(null);
- setChildren(null);
- //父節點更新關鍵字
- parent.updateInsert(tree);
- setParent(null);
- //如果是根節點
- }else {
- isRoot = false;
- Node parent = new Node(false, true);
- tree.setRoot(parent);
- left.setParent(parent);
- right.setParent(parent);
- parent.getChildren().add(left);
- parent.getChildren().add(right);
- setEntries(null);
- setChildren(null);
- //更新根節點
- parent.updateInsert(tree);
- }
- }
- }
- /** 調整節點關鍵字*/
- protectedstaticvoid validate(Node node, BplusTree tree) {
- // 如果關鍵字個數與子節點個數相同
- if (node.getEntries().size() == node.getChildren().size()) {
- for (int i = 0; i < node.getEntries().size(); i++) {
- Comparable key = node.getChildren().get(i).getEntries().get(0).getKey();
- if (node.getEntries().get(i).getKey().compareTo(key) != 0) {
- node.getEntries().remove(i);
- node.getEntries().add(i, new SimpleEntry(key, null));
- if(!node.isRoot()){
- validate(node.getParent(), tree);
- }
- }
- }
- // 如果子節點數不等於關鍵字個數但仍大於M / 2並且小於M,並且大於2
- } elseif (node.isRoot() && node.getChildren().size() >= 2
- ||node.getChildren().size() >= tree.getOrder() / 2
- && node.getChildren().size() <= tree.getOrder()
- && node.getChildren().size() >= 2) {
- node.getEntries().clear();
- for (int i = 0; i < node.getChildren().size(); i++) {
- Comparable key = node.getChildren().get(i).getEntries().get(0).getKey();
- node.getEntries().add(new SimpleEntry(key, null));
- if (!node.isRoot()) {
- validate(node.getParent(), tree);
- }
- }
- }
- }
- /** 刪除節點後中間節點的更新*/
- protectedvoid updateRemove(BplusTree tree) {
- validate(this, tree);
- // 如果子節點數小於M / 2或者小於2,則需要合併節點
- if (children.size() < tree.getOrder() / 2 || children.size() < 2) {
- if (isRoot) {
- // 如果是根節點並且子節點數大於等於2,OK
- if (children.size() >= 2) {
- return;
- // 否則與子節點合併
- } else {
- Node root = children.get(0);
- tree.setRoot(root);
- root.setParent(null);
- root.setRoot(true);
- setEntries(null);
- setChildren(null);
- }
- } else {
- //計算前後節點
- int currIdx = parent.getChildren().indexOf(this);
- int prevIdx = currIdx - 1;
- int nextIdx = currIdx + 1;
- Node previous = null, next = null;
- if (prevIdx >= 0) {
- previous = parent.getChildren().get(prevIdx);
- }
- if (nextIdx < parent.getChildren().size()) {
- next = parent.getChildren().get(nextIdx);
- }
- // 如果前節點子節點數大於M / 2並且大於2,則從其處借補
- if (previous != null
- && previous.getChildren().size() > tree.getOrder() / 2
- && previous.getChildren().size() > 2) {
- //前葉子節點末尾節點新增到首位
- int idx = previous.getChildren().size() - 1;
- Node borrow = previous.getChildren().get(idx);
- previous.getChildren().remove(idx);
- borrow.setParent(this);
- children.add(0, borrow);
- validate(previous, tree);
- validate(this, tree);
- parent.updateRemove(tree);
- // 如果後節點子節點數大於M / 2並且大於2,則從其處借補
- } elseif (next != null
- && next.getChildren().size() > tree.getOrder() / 2
- && next.getChildren().size() > 2) {
- //後葉子節點首位新增到末尾
- Node borrow = next.getChildren().get(0);
- next.getChildren().remove(0);
- borrow.setParent(this);
- children.add(borrow);
- validate(next, tree);
- validate(this, tree);
- parent.updateRemove(tree);
- // 否則需要合併節點
- } else {
- // 同前面節點合併
- if (previous != null
- && (previous.getChildren().size() <= tree.getOrder() / 2 || previous.getChildren().size() <= 2)) {
- for (int i = previous.getChildren().size() - 1; i >= 0; i--) {
- Node child = previous.getChildren().get(i);
- children.add(0, child);
- child.setParent(this);
- }
- previous.setChildren(null);
- previous.setEntries(null);
- previous.setParent(null);
- parent.getChildren().remove(previous);
- validate(this, tree);
- parent.updateRemove(tree);
- // 同後面節點合併
- } elseif (next != null
- && (next.getChildren().size() <= tree.getOrder() / 2 || next.getChildren().size() <= 2)) {
- for (int i = 0; i < next.getChildren().size(); i++) {
- Node child = next.getChildren().get(i);
- children.add(child);
- child.setParent(this);
- }
- next.setChildren(null);
- next.setEntries(null);
- next.setParent(null);
- parent.getChildren().remove(next);
- validate(this, tree);
- parent.updateRemove(tree);
- }
- }
- }
- }
- }
- publicvoid remove(Comparable key, BplusTree tree){
- //如果是葉子節點
- if (isLeaf){
- //如果不包含該關鍵字,則直接返回
- if (!contains(key)){
- return;
- }
- //如果既是葉子節點又是跟節點,直接刪除
- if (isRoot) {
- remove(key);
- }else {
- //如果關鍵字數大於M / 2,直接刪除
- if (entries.size() > tree.getOrder() / 2 && entries.size() > 2) {
- remove(key);
- }else {
- //如果自身關鍵字數小於M / 2,並且前節點關鍵字數大於M / 2,則從其處借補
- if (previous != null
- && previous.getEntries().size() > tree.getOrder() / 2
- && previous.getEntries().size() > 2
- && previous.getParent() == parent) {
- int size = previous.getEntries().size();
- Entry<Comparable, Object> entry = previous.getEntries().get(size - 1);
- previous.getEntries().remove(entry);
- //新增到首位
- entries.add(0, entry);
- remove(key);
- //如果自身關鍵字數小於M / 2,並且後節點關鍵字數大於M / 2,則從其處借補
- }elseif (next != null
- && next.getEntries().size() > tree.getOrder() / 2
- && next.getEntries().size() > 2
- && next.getParent() == parent) {
- Entry<Comparable, Object> entry = next.getEntries().get(0);
- next.getEntries().remove(entry);
- //新增到末尾
- entries.add(entry);
- remove(key);
- //否則需要合併葉子節點
- }else {
- //同前面節點合併
- if (previous != null
- && (previous.getEntries().size() <= tree.getOrder() / 2 || previous.getEntries().size() <= 2)
- && previous.getParent() == parent) {
- for (int i = previous.getEntries().size() - 1; i >=0; i--) {
- //從末尾開始新增到首位
- entries.add(0, previous.getEntries().get(i));
- }
- remove(key);
- previous.setParent(null);
- previous.setEntries(null);
- parent.getChildren().remove(previous);
- //更新連結串列
- if (previous.getPrevious() != null) {
- Node temp = previous;
- temp.getPrevious().setNext(this);
- previous = temp.getPrevious();
- temp.setPrevious(null);
- temp.setNext(null);
- }else {
- tree.setHead(this);
- previous.setNext(null);
- previous = null;
- }
- //同後面節點合併
- }else if(next != null
- && (next.getEntries().size() <= tree.getOrder() / 2 || next.getEntries().size() <= 2)
- && next.getParent() == parent){
- for (int i = 0; i < next.getEntries().size(); i++) {
- //從首位開始新增到末尾
- entries.add(next.getEntries().get(i));
- }
- remove(key);
- next.setParent(null);
- next.setEntries(null);
- parent.getChildren().remove(next);
- //更新連結串列
- if (next.getNext() != null) {
- Node temp = next;
- temp.getNext().setPrevious(this);
- next = temp.getNext();
- temp.setPrevious(null);
- temp.setNext(null);
- }else {
- next.setPrevious(null);
- next = null;
- }
- }
- }
- }
- parent.updateRemove(tree);
- }
- //如果不是葉子節點
- }else {
- //如果key小於等於節點最左邊的key,沿第一個子節點繼續搜尋
- if (key.compareTo(entries.get(0).getKey()) <= 0) {
- children.get(0).remove(key, tree);
- //如果key大於節點最右邊的key,沿最後一個子節點繼續搜尋
- }elseif (key.compareTo(entries.get(entries.size()-