liwanchun_xd

B树（二叉搜索树）定义：
1）、每个非叶子节点至多有两个子节点。
2）、每个节点都存储关键字值。
3）、其左子节点的关键字值小于该节点，且右子节点的关键字值大于或等于该节点。

简略代码实现：
/**
* 节点类
*/
class Node{
public int key;
public int data;
public Node leftChild;
public Node rightChild;

public Node(int key, int data){
this.key = key;
this.data = data;
this.leftChild = null;
this.rightChild = null;
}

public void display(){
System.out.println("key: " + key + ", data: " + data);
}
}

/**
* B树类
*/
class Tree{
public Node root;

public void insert(int key, int data){
Node newNode = new Node(key, data);

if (root == null){
root = newNode;
}else{
Node current = root;
Node parent = null;
while (true){
parent = current;
if (key < current.key){
current = current.leftChild;
if (current == null){
parent.leftChild = newNode;
return;
}
}else{
current = current.rightChild;
if (current == null){
parent.rightChild = newNode;
return;
}
}
}
}
}

/** 只实现有一个节点的删除 */
public boolean delete(int key){
Node current = root;
Node parent = null;
boolean isLeftChild = false;

while (current.key != key){
parent = current;
if (key < current.key){
current = current.leftChild;
isLeftChild = true;
}else{
current = current.rightChild;
isLeftChild = false;
}
}

if (current == null){
return false;
}

/** 无子节点 */
if (current.leftChild == null && current.rightChild == null){
if (current == root){
root = null;
}else if (isLeftChild){
parent.leftChild = null;
}else{
parent.rightChild = null;
}
}
/** 仅有右节点 */
else if ((current.leftChild == null && current.rightChild != null)){
if (current == root){
root = current.rightChild;
}else if (isLeftChild){
parent.leftChild = current.rightChild;
}else{
parent.rightChild = current.rightChild;
}
}else if ((current.leftChild != null && current.rightChild == null)){
if (current == root){
root = null;
}else if (isLeftChild){
parent.leftChild = current.leftChild;
}else{
parent.rightChild = current.leftChild;
}
}
return true;
}

public Node find(int key){
Node current = root;
while (current != null){
if (current.key == key){
break;
}else if (key < current.key){
current = current.leftChild;
}else{
current = current.rightChild;
}
}

return current;
}

/** 中序 */
public void inOrder(Node localNode){
if (localNode != null){
inOrder(localNode.leftChild);
System.out.println("key: " + localNode.key + ", data: " + localNode.data);
inOrder(localNode.rightChild);
}

}

}

public class BTree {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Tree newTree = new Tree();
newTree.insert(5, 5);
newTree.insert(1, 1);
newTree.insert(2, 2);
newTree.insert(8, 8);
newTree.insert(9, 9);
newTree.insert(7, 7);

newTree.delete(1);
newTree.inOrder(newTree.root);
}

}