Java二叉樹（一）--定義及前序、中序、後序、層次遍歷及求高度的實現

package binarytree;

import java.util.LinkedList;
import java.util.Queue;

/**
 * @author Gavenyeah
 * @date Time: 2016年4月10日下午10:14:08
 * @des:
 */
public class BinaryTree {
    Node root = null;// 二叉樹的根節點

    // 二叉樹的節點插入
    public void insert(int val) {
        Node newNode = new Node(val);
        if (root == null) {
            root = newNode;
            return;
        }
        Node current = root;
        Node parent = null;
        while (true) {
            parent = current;
            if (val < current.data) {
                current = current.left;
                if (current == null) {
                    parent.left = newNode;
                    return;
                }
            } else if (val > current.data) {
                current = current.right;
                if (current == null) {
                    parent.right = newNode;
                    return;
                }
            }
        }
    }

    // 利用數組建立（中序）排序二叉樹
    public void buildTree(int arrays[]) {
        for (int i = 0; i < arrays.length; i++) {
            insert(arrays[i]);
        }
    }

    // 中序遍歷二叉樹
    public void inOrder(Node head) {
        if (head != null) {
            inOrder(head.left);
            visit(head);
            inOrder(head.right);
        }
    }
    public void inOrder() {
        this.inOrder(this.root);
    }

    public void preOrder(Node head) {
        if (head != null) {
            visit(head);
            preOrder(head.left);
            preOrder(head.right);
        }
    }
    public void preOrder() {
        this.preOrder(this.root);
    }

    public void postOrder(Node head) {
        if (head != null) {
            postOrder(head.left);
            postOrder(head.right);
            visit(head);
        }
    }
    public void postOrder() {
        this.postOrder(this.root);
    }

    //層次遍歷二叉樹
    public void layerOrder(Node head){
        if(head==null){
            return ;
        }
        Queue<Node>queue=new LinkedList<Node>();
        queue.add(head);
        while(queue.size()>0){
            head=queue.poll();
            visit(head);
            if(head.left!=null){
                queue.add(head.left);
            }
            if(head.right!=null){
                queue.add(head.right);
            }
        }
    }
    public void layerOrder(){
        this.layerOrder(this.root);
    }
    // 層次遍歷輸出樹的高度
    public int levelOfTree(Node head) {
        int level = 0;// 記錄樹的層數
        int front = 0;// 標記當前取出的節點標號
        int rear = 0;// 標記當前存入隊列的節點標號
        int last = 1;// 記錄當前行最後一個節點的編號，初始值爲1，即第一層最後一個節點的編號爲1
        Queue<Node> queue = new LinkedList<Node>();
        queue.add(head);
        rear++;// 根節點加入隊列
        while (queue.size()>0) {
            head = queue.poll();
            front++;
            if (head.left != null) {
                queue.add(head.left);
                rear++;
            }
            if (head.right != null) {
                queue.add(head.right);
                rear++;
            }
            // 取出的節點數到達每層最後一個節點後，改變樹的層數，並使last等於下一層最後一個節點
            if (front == last) {
                level++;
                last = rear;
            }
        }
        return level;
    }
    public int levelOfTree() {
        return this.levelOfTree(this.root);
    }

    public void visit(Node node) {
        System.out.print(node.data + "\t");
    }
}

class Node {
    int data;
    Node left;
    Node right;
    public Node(int data) {
        this.data = data;
        this.left = null;
        this.right = null;
    }
}