import java.util.ArrayDeque;

import java.util.Queue;

import java.util.Stack;

//二叉树的建树，前中后 递归非递归遍历 层序遍历

//Node节点

class Node {

int element;

Node left;

Node right;

public Node() {

}

public Node(int element) {

this.element = element;

}

}

// BinaryTree

public class Tree {

// creat tree from array

public static Node creatTree(int[] data, int i) {

if (i >= data.length || data[i] == -1)

return null;

Node temp = new Node(data[i]);

temp.left = creatTree(data, i * 2 + 1);

temp.right = creatTree(data, i * 2 + 2);

return temp;

}

// pre前序遍历递归

public static void pre(Node temp) {

if (temp == null)

return;

System.out.print(temp.element + " ");

pre(temp.left);

pre(temp.right);

}

// mid中序遍历递归

public static void mid(Node temp) {

if (temp == null)

return;

mid(temp.left);

System.out.print(temp.element + " ");

mid(temp.right);

}

// last后序遍历递归

public static void last(Node temp) {

if (temp == null)

return;

last(temp.left);

last(temp.right);

System.out.print(temp.element + " ");

}

// pre1前序遍历非递归

public static void pre1(Node temp) {

Stack stack = new Stack<>();

while (temp != null || !stack.isEmpty()) {

while (temp != null) {

stack.push(temp);

System.out.print(temp.element + " ");

temp = temp.left;

}

if (!stack.isEmpty()) {

temp = stack.pop().right;

}

}

}

// mid1中序遍历非递归

public static void mid1(Node temp) {

Stack stack = new Stack<>();

while (temp != null || !stack.isEmpty()) {

while (temp != null) {

stack.push(temp);

temp = temp.left;

}

if (!stack.isEmpty()) {

temp = stack.pop();

System.out.print(temp.element + " ");

temp = temp.right;

}

}

}

// last1后序遍历非递归

public static void last1(Node temp) {

Stack stack = new Stack<>();

Stack stack2 = new Stack<>();

while (temp != null || !stack.isEmpty()) {

while (temp != null) {

stack.push(temp);

stack2.push(temp);

temp = temp.right;

}

if (!stack.isEmpty()) {

temp = stack.pop().left;

}

}

while (!stack2.isEmpty())

System.out.print(stack2.pop().element + " ");

}

// ceng层序遍历

public static void ceng(Node temp) {

if (temp == null)

return;

Queue queue = new ArrayDeque<>();

queue.offer(temp);

while (!queue.isEmpty()) {

temp = queue.poll();

System.out.print(temp.element + " ");

if (temp.left != null)

queue.offer(temp.left);

if (temp.right != null)

queue.offer(temp.right);

}

}

// Demo

public static void main(String[] args) {

int[] array = { 1, 2, 3, 4, 5, 6, 7, -1, -1, 10, -1, -1, 13 };

Node tree = creatTree(array, 0);

System.out.println("脚本之家测试结果：");

pre(tree);

System.out.println();

pre1(tree);

System.out.println();

mid(tree);

System.out.println();

mid1(tree);

System.out.println();

last(tree);

System.out.println();

last1(tree);

System.out.println();

ceng(tree);

}

}

运行结果：

希望本文所述对大家java程序设计有所帮助。

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