最近有人老是问我在Java中如何实现Tree的数据结构算法，今天在网上看了一篇关于这方面的代码，拿出来和大家分享一下吧！
代码实现[一]部分
package ChapterEight;
class Tree {
class Node {
public long value;
public Node leftChild;
public Node rightChild;
public Node(long value) {
this.value = value;
leftChild = null;
rightChild = null;
}
}
public Node root;
public Tree() {
root = null;
}
// 向树中插入一个节点
public void insert(long value) {
Node newNode = new Node(value);
// 树是空的
if (root == null)
root = newNode;
else {
Node current = root;
Node parentNode;
while (true) {
parentNode = current;
if (value < current.value) {
current = current.leftChild;
// 要插入的节点为左孩子节点
if (current == null) {
parentNode.leftChild = newNode;
return;
}
} else {
// 要插入的节点为右孩子节点
current = current.rightChild;
if (current == null) {
parentNode.rightChild = newNode;
return;
}
}
}
}
}
// 先续遍历树中的所有节点
public void preOrder(Node currentRoot) {
if (currentRoot != null) {
System.out.print(currentRoot.value + " ");
preOrder(currentRoot.leftChild);
preOrder(currentRoot.rightChild);
}
}
// 中续遍历树中的所有节点
public void inOrder(Node currentNode) {
if (currentNode != null) {
inOrder(currentNode.leftChild);
System.out.print(currentNode.value + " ");
inOrder(currentNode.rightChild);
}
}
// 后续遍历树中的所有节点
public void postOrder(Node currentNode) {
if (currentNode != null) {
postOrder(currentNode.leftChild);
postOrder(currentNode.rightChild);
System.out.print(currentNode.value + " ");
}
}
public void traverse(int traverseType) {
switch (traverseType) {
case 1:
preOrder(root);
break;
case 2:
inOrder(root);
break;
case 3:
postOrder(root);
break;
default:
break;
}
// 依据树节点的值删除树中的一个节点
public boolean delete(int value) {
// 遍历树过程中的当前节点
Node current = root;
// 要删除节点的父节点
Node parent = root;
// 记录树的节点为左孩子节点或右孩子节点
boolean isLeftChild = true;
while (current.value != value) {
parent = current;
// 要删除的节点在当前节点的左子树里
if (value < current.value) {
isLeftChild = true;
current = current.leftChild;
}
// 要删除的节点在当前节点的右子树里
else {
isLeftChild = false;
current = current.rightChild;
}
// 在树中没有找到要删除的节点
if (current == null)
return false;
}
// 要删除的节点为叶子节点
if (current.leftChild == null && current.rightChild == null) {
// 要删除的节点为根节点
if (current == root)
root = null;
// 要删除的节点为左孩子节点
else if (isLeftChild)
parent.leftChild = null;
// 要删除的节点为右孩子节点
else
parent.rightChild = null;
}
// 要删除的节点有左孩子节点，没有右孩子节点
else if (current.rightChild == null) {
// 要删除的节点为根节点
if (current == null)
root = current.leftChild;
// 要删除的节点为左孩子节点
else if (isLeftChild)
parent.leftChild = current.leftChild;
// 要删除的节点为右孩子节点
else
parent.rightChild = current.leftChild;
}
// 要删除的节点没有左孩子节点，有右孩子节点
else if (current.leftChild == null) {
// 要删除的节点为根节点
if (current == root)
root = root.rightChild;
// 要删除的节点为左孩子节点
else if (isLeftChild)
parent.leftChild = current.rightChild;
// 要删除的节点为右孩子节点
else
parent.rightChild = current.rightChild;
}
// 要删除的接节点既有左孩子节点又有右孩子节点
else {
Node successor = getSuccessor(current);
// 要删除的节点为根节点
if (current == root)
root = successor;
// 要删除的节点为左孩子节点
else if (isLeftChild)
parent.leftChild = successor;
// 要删除的节点为右孩子节点
else
parent.rightChild = successor;
}
return true;
}
// 找到要删除节点的替补节点
private Node getSuccessor(Node delNode) {
// 替补节点的父节点
Node successorParent = delNode;
// 删除节点的替补节点
Node successor = delNode;
Node current = delNode.rightChild;
while (current != null) {
// successorParent指向当前节点的上一个节点
successorParent = successor;
// successor变为当前节点
successor = current;
current = current.leftChild;
}
// 替补节点的右孩子节点不为空
if (successor != delNode.rightChild) {
successorParent.leftChild = successor.rightChild;
successor.rightChild = delNode.rightChild;
}
return successor;
}
}
public class TreeApp {
public static void main(String[] args) {
Tree tree = new Tree();
tree.insert(8);
tree.insert(50);
tree.insert(45);
tree.insert(21);
tree.insert(32);
tree.insert(18);
tree.insert(37);
tree.insert(64);
tree.insert(88);
tree.insert(5);
tree.insert(4);
tree.insert(7);
System.out.print("PreOrder : ");
tree.traverse(1);
System.out.println();
System.out.print("InOrder : ");
tree.traverse(2);
System.out.println();
System.out.print("PostOrder : ");
tree.traverse(3);
System.out.println();
System.out.println(tree.delete(7));
System.out.print("PreOrder : ");
tree.traverse(1);
System.out.println();
System.out.print("InOrder : ");
tree.traverse(2);
System.out.println();
System.out.print("PostOrder : ");
tree.traverse(3);
System.out.println();
}
}