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java遍历二叉树,java遍历二叉树代码

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JAVA:在一棵二叉链表表示的二叉树中,采用哪种遍历算法操作: 1.输出叶子结点 2求叶子结点个数 我要编码

晕死了,人家说用java实现

int i = 0;

void getChildren(int parentId) {

List list = "select * from table where parentId = "+parendId; //从数据库获取子节点

if(list.size() 0){

for(list) { //遍历list,递归取子节点

getChildren("aaa"); //递归取子节点

}

}else { //如果list为空,说明为子节点

System.out.println(parentId); //打印子节点

i++;

}

}

java一个关于二叉树的简单编程题

定义一个结点类:

public class Node {

private int value;

private Node leftNode;

private Node rightNode;

public Node getRightNode() {

return rightNode;

}

public void setRightNode(Node rightNode) {

this.rightNode = rightNode;

}

public int getValue() {

return value;

}

public void setValue(int value) {

this.value = value;

}

public Node getLeftNode() {

return leftNode;

}

public void setLeftNode(Node leftNode) {

this.leftNode = leftNode;

}

}

初始化结点树:

public void initNodeTree()

{

int nodeNumber;

HashMapString, Integer map = new HashMapString, Integer();

Node nodeTree = new Node();

Scanner reader = new Scanner(System.in);

nodeNumber = reader.nextInt();

for(int i = 0; i nodeNumber; i++) {

int value = reader.nextInt();

String str = reader.next();

map.put(str, value);

}

if (map.containsKey("#")) {

int value = map.get("#");

nodeTree.setValue(value);

setChildNode(map, value, nodeTree);

}

preTraversal(nodeTree);

}

private void setChildNode(HashMapString, Integer map, int nodeValue, Node parentNode) {

int value = 0;

if (map.containsKey("L" + nodeValue)) {

value = map.get("L" + nodeValue);

Node leftNode = new Node();

leftNode.setValue(value);

parentNode.setLeftNode(leftNode);

setChildNode(map, value, leftNode);

}

if (map.containsKey("R" + nodeValue)) {

value = map.get("R" + nodeValue);

Node rightNode = new Node();

rightNode.setValue(value);

parentNode.setRightNode(rightNode);

setChildNode(map, value, rightNode);

}

}

前序遍历该结点树:

public void preTraversal(Node nodeTree) {

if (nodeTree != null) {

System.out.print(nodeTree.getValue() + "\t");

preTraversal(nodeTree.getLeftNode());

preTraversal(nodeTree.getRightNode());

}

}

写一个java层次遍历二叉树,简单点就可以,我要的是代码,不是纯文字说明

public class BinaryNode {

Object element;

BinaryNode left;

BinaryNode right;

}

import java.util.*;

public class Queue {

protected LinkedList list;

// Postcondition: this Queue object has been initialized.

public Queue() {

list = new LinkedList();

} // default constructor

// Postcondition: the number of elements in this Queue object has been

// returned.

public int size() {

return list.size();

} // method size

// Postcondition: true has been returned if this Queue object has no

// elements. Otherwise, false has been returned.

public boolean isEmpty() {

return list.isEmpty();

} // method isEmpty

// Postconditon: A copy of element has been inserted at the back of this

// Queue object. The averageTime (n) is constant and

// worstTime (n) is O (n).

public void enqueue(Object element) {

list.addLast(element);

} // method enqueue

// Precondition: this Queue object is not empty. Otherwise,

// NoSuchElementException will be thrown.

// Postcondition: The element that was at the front of this Queue object -

// just before this method was called -- has been removed

// from this Queue object and returned.

public Object dequeue() {

return list.removeFirst();

} // method dequeue

// Precondition: this Queue object is not empty. Otherwise,

// NoSuchElementException will be thrown.

// Postcondition: the element at index 0 in this Queue object has been

// returned.

public Object front() {

return list.getFirst();

} // method front

} // Queue class

import java.io.IOException;

public class BinaryTree {

BinaryNode root;

public BinaryTree() {

super();

// TODO 自动生成构造函数存根

root=this.createPre();

}

public BinaryNode createPre()

//按照先序遍历的输入方法,建立二叉树

{

BinaryNode t=null;

char ch;

try {

ch = (char)System.in.read();

if(ch==' ')

t=null;

else

{

t=new BinaryNode();

t.element=(Object)ch;

t.left=createPre();

t.right=createPre();

}

} catch (IOException e) {

// TODO 自动生成 catch 块

e.printStackTrace();

}

return t;

}

public void inOrder()

{

this.inOrder(root);

}

public void inOrder(BinaryNode t)

//中序遍历二叉树

{

if(t!=null)

{

inOrder(t.left);

System.out.print(t.element);

inOrder(t.right);

}

}

public void postOrder()

{

this.postOrder(root);

}

public void postOrder(BinaryNode t)

//后序遍历二叉树

{

if(t!=null)

{

postOrder(t.left);

System.out.print(t.element);

postOrder(t.right);

}

}

public void preOrder()

{

this.preOrder(root);

}

public void preOrder(BinaryNode t)

//前序遍历二叉树

{

if(t!=null)

{

System.out.print(t.element);

preOrder(t.left);

preOrder(t.right);

}

}

public void breadthFirst()

{

Queue treeQueue=new Queue();

BinaryNode p;

if(root!=null)

treeQueue.enqueue(root);

while(!treeQueue.isEmpty())

{

System.out.print(((BinaryNode)(treeQueue.front())).element);

p=(BinaryNode)treeQueue.dequeue();

if(p.left!=null)

treeQueue.enqueue(p.left);

if(p.right!=null)

treeQueue.enqueue(p.right);

}

}

}

public class BinaryTreeTest {

/**

* @param args

*/

public static void main(String[] args) {

// TODO 自动生成方法存根

BinaryTree tree = new BinaryTree();

System.out.println("先序遍历:");

tree.preOrder();

System.out.println();

System.out.println("中序遍历:");

tree.inOrder();

System.out.println();

System.out.println("后序遍历:");

tree.postOrder();

System.out.println();

System.out.println("层次遍历:");

tree.breadthFirst();

System.out.println();

}

}

java实现二叉树层次遍历

import java.util.ArrayList;

public class TreeNode {

private TreeNode leftNode;

private TreeNode rightNode;

private String nodeName;

public TreeNode getLeftNode() {

return leftNode;

}

public void setLeftNode(TreeNode leftNode) {

this.leftNode = leftNode;

}

public TreeNode getRightNode() {

return rightNode;

}

public void setRightNode(TreeNode rightNode) {

this.rightNode = rightNode;

}

public String getNodeName() {

return nodeName;

}

public void setNodeName(String nodeName) {

this.nodeName = nodeName;

}

public static int level=0;

public static void findNodeByLevel(ArrayListTreeNode nodes){

if(nodes==null||nodes.size()==0){

return ;

}

level++;

ArrayListTreeNode temp = new ArrayList();

for(TreeNode node:nodes){

System.out.println("第"+level+"层:"+node.getNodeName());

if(node.getLeftNode()!=null){

temp.add(node.getLeftNode());

}

if(node.getRightNode()!=null){

temp.add(node.getRightNode());

}

}

nodes.removeAll(nodes);

findNodeByLevel(temp);

}

/**

* @param args

*/

public static void main(String[] args) {

// TODO Auto-generated method stub

TreeNode root = new TreeNode();

root.setNodeName("root");

TreeNode node1 = new TreeNode();

node1.setNodeName("node1");

TreeNode node3 = new TreeNode();

node3.setNodeName("node3");

TreeNode node7 = new TreeNode();

node7.setNodeName("node7");

TreeNode node8 = new TreeNode();

node8.setNodeName("node8");

TreeNode node4 = new TreeNode();

node4.setNodeName("node4");

TreeNode node2 = new TreeNode();

node2.setNodeName("node2");

TreeNode node5 = new TreeNode();

node5.setNodeName("node5");

TreeNode node6 = new TreeNode();

node6.setNodeName("node6");

root.setLeftNode(node1);

node1.setLeftNode(node3);

node3.setLeftNode(node7);

node3.setRightNode(node8);

node1.setRightNode(node4);

root.setRightNode(node2);

node2.setLeftNode(node5);

node2.setRightNode(node6);

ArrayListTreeNode nodes = new ArrayListTreeNode();

nodes.add(root);

findNodeByLevel(nodes);

}

}

java构建二叉树算法

//******************************************************************************************************//

//*****本程序包括简单的二叉树类的实现和前序,中序,后序,层次遍历二叉树算法,*******//

//******以及确定二叉树的高度,制定对象在树中的所处层次以及将树中的左右***********//

//******孩子节点对换位置,返回叶子节点个数删除叶子节点,并输出所删除的叶子节点**//

//*******************************CopyRight By phoenix*******************************************//

//************************************Jan 12,2008*************************************************//

//****************************************************************************************************//

public class BinTree {

public final static int MAX=40;

private Object data; //数据元数

private BinTree left,right; //指向左,右孩子结点的链

BinTree []elements = new BinTree[MAX];//层次遍历时保存各个节点

int front;//层次遍历时队首

int rear;//层次遍历时队尾

public BinTree()

{

}

public BinTree(Object data)

{ //构造有值结点

this.data = data;

left = right = null;

}

public BinTree(Object data,BinTree left,BinTree right)

{ //构造有值结点

this.data = data;

this.left = left;

this.right = right;

}

public String toString()

{

return data.toString();

}//前序遍历二叉树

public static void preOrder(BinTree parent){

if(parent == null)

return;

System.out.print(parent.data+" ");

preOrder(parent.left);

preOrder(parent.right);

}//中序遍历二叉树

public void inOrder(BinTree parent){

if(parent == null)

return;

inOrder(parent.left);

System.out.print(parent.data+" ");

inOrder(parent.right);

}//后序遍历二叉树

public void postOrder(BinTree parent){

if(parent == null)

return;

postOrder(parent.left);

postOrder(parent.right);

System.out.print(parent.data+" ");

}// 层次遍历二叉树

public void LayerOrder(BinTree parent)

{

elements[0]=parent;

front=0;rear=1;

while(frontrear)

{

try

{

if(elements[front].data!=null)

{

System.out.print(elements[front].data + " ");

if(elements[front].left!=null)

elements[rear++]=elements[front].left;

if(elements[front].right!=null)

elements[rear++]=elements[front].right;

front++;

}

}catch(Exception e){break;}

}

}//返回树的叶节点个数

public int leaves()

{

if(this == null)

return 0;

if(left == nullright == null)

return 1;

return (left == null ? 0 : left.leaves())+(right == null ? 0 : right.leaves());

}//结果返回树的高度

public int height()

{

int heightOfTree;

if(this == null)

return -1;

int leftHeight = (left == null ? 0 : left.height());

int rightHeight = (right == null ? 0 : right.height());

heightOfTree = leftHeightrightHeight?rightHeight:leftHeight;

return 1 + heightOfTree;

}

//如果对象不在树中,结果返回-1;否则结果返回该对象在树中所处的层次,规定根节点为第一层

public int level(Object object)

{

int levelInTree;

if(this == null)

return -1;

if(object == data)

return 1;//规定根节点为第一层

int leftLevel = (left == null?-1:left.level(object));

int rightLevel = (right == null?-1:right.level(object));

if(leftLevel0rightLevel0)

return -1;

levelInTree = leftLevelrightLevel?rightLevel:leftLevel;

return 1+levelInTree;

}

//将树中的每个节点的孩子对换位置

public void reflect()

{

if(this == null)

return;

if(left != null)

left.reflect();

if(right != null)

right.reflect();

BinTree temp = left;

left = right;

right = temp;

}// 将树中的所有节点移走,并输出移走的节点

public void defoliate()

{

String innerNode = "";

if(this == null)

return;

//若本节点是叶节点,则将其移走

if(left==nullright == null)

{

System.out.print(this + " ");

data = null;

return;

}

//移走左子树若其存在

if(left!=null){

left.defoliate();

left = null;

}

//移走本节点,放在中间表示中跟移走...

innerNode += this + " ";

data = null;

//移走右子树若其存在

if(right!=null){

right.defoliate();

right = null;

}

}

/**

* @param args

*/

public static void main(String[] args) {

// TODO Auto-generated method stub

BinTree e = new BinTree("E");

BinTree g = new BinTree("G");

BinTree h = new BinTree("H");

BinTree i = new BinTree("I");

BinTree d = new BinTree("D",null,g);

BinTree f = new BinTree("F",h,i);

BinTree b = new BinTree("B",d,e);

BinTree c = new BinTree("C",f,null);

BinTree tree = new BinTree("A",b,c);

System.out.println("前序遍历二叉树结果: ");

tree.preOrder(tree);

System.out.println();

System.out.println("中序遍历二叉树结果: ");

tree.inOrder(tree);

System.out.println();

System.out.println("后序遍历二叉树结果: ");

tree.postOrder(tree);

System.out.println();

System.out.println("层次遍历二叉树结果: ");

tree.LayerOrder(tree);

System.out.println();

System.out.println("F所在的层次: "+tree.level("F"));

System.out.println("这棵二叉树的高度: "+tree.height());

System.out.println("--------------------------------------");

tree.reflect();

System.out.println("交换每个节点的孩子节点后......");

System.out.println("前序遍历二叉树结果: ");

tree.preOrder(tree);

System.out.println();

System.out.println("中序遍历二叉树结果: ");

tree.inOrder(tree);

System.out.println();

System.out.println("后序遍历二叉树结果: ");

tree.postOrder(tree);

System.out.println();

System.out.println("层次遍历二叉树结果: ");

tree.LayerOrder(tree);

System.out.println();

System.out.println("F所在的层次: "+tree.level("F"));

System.out.println("这棵二叉树的高度: "+tree.height());

}

java Map 怎么遍历

java Map 遍历一般有四种方式

方式一: 这是最常见的并且在大多数情况下也是最可取的遍历方式。在键值都需要时使用。

方式二: 在for-each循环中遍历keys或values。

如果只需要map中的键或者值,你可以通过keySet或values来实现遍历,而不是用entrySet。

该方法比entrySet遍历在性能上稍好(快了10%),而且代码更加干净。

方式三:使用Iterator遍历

使用泛型:

不使用泛型:

你也可以在keySet和values上应用同样的方法。

方法四:  通过键找值遍历(效率低)

作为方法一的替代,这个代码看上去更加干净;但实际上它相当慢且无效率。

因为从键取值是耗时的操作(与方法一相比,在不同的Map实现中该方法慢了20%~200%)。如果安装了FindBugs,它会做出检查并警告你关于哪些是低效率的遍历。所以尽量避免使用。

总结:

如果仅需要键(keys)或值(values)使用方法二。

如果所使用的语言版本低于java 5,或是打算在遍历时删除entries,必须使用方法三。

否则使用方法一(键值都要)。

扩展资料:

类似的遍历算法:

二叉树的遍历算法

1、先(根)序遍历的递归算法定义:

若二叉树非空,则依次执行如下操作:

⑴ 访问根结点;

⑵ 遍历左子树;

⑶ 遍历右子树。

2、中(根)序遍历的递归算法定义:

若二叉树非空,则依次执行如下操作:

⑴遍历左子树;

⑵访问根结点;

⑶遍历右子树。

3、后(根)序遍历得递归算法定义:

若二叉树非空,则依次执行如下操作:

⑴遍历左子树;

⑵遍历右子树;

⑶访问根结点。

参考资料:百度百科——Java

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