为什么需要树这种数据结构
概念
代码实现
//创建HeroNode节点
class HeroNode{
private int no;
private String name;
private HeroNode left;
private HeroNode right;
public HeroNode(int no, String name) {
this.no = no;
this.name = name;
}
@Override
public String toString() {
return "HeroNode{" +
"no=" + no +
", name='" + name + '\'' +
'}';
}
//前序遍历
public void preOrder(){
System.out.println(this);
//递归向左子树前序遍历
if(this.left != null){
this.left.preOrder();
}
//递归向右子树前序遍历
if(this.right != null){
this.right.preOrder();
}
}
//中序遍历
public void infixOrder(){
if(this.left != null){
this.left.infixOrder();
}
System.out.println(this);
if(this.right != null){
this.right.infixOrder();
}
}
//后续遍历
public void postOrder(){
if(this.left != null){
this.left.infixOrder();
}
if(this.right != null){
this.right.infixOrder();
}
System.out.println(this);
}
public int getNo() {
return no;
}
public void setNo(int no) {
this.no = no;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public HeroNode getLeft() {
return left;
}
public void setLeft(HeroNode left) {
this.left = left;
}
public HeroNode getRight() {
return right;
}
public void setRight(HeroNode right) {
this.right = right;
}
}
//定义BinaryTree二叉树
class BinaryTree{
private HeroNode root;
public void setRoot(HeroNode root) {
this.root = root;
}
//前序遍历
public void preOrder(){
if(this.root != null){
this.root.preOrder();
}else {
System.out.println("二叉树为空,无法遍历");
}
}
//中序遍历
public void infixOrder(){
if(this.root != null){
this.root.infixOrder();
}else {
System.out.println("二叉树为空,无法遍历");
}
}
//后续遍历
public void postOrder(){
if(this.root != null){
this.root.postOrder();
}else {
System.out.println("二叉树为空,无法遍历");
}
}
}
public class BinaryTreeDemo {
public static void main(String[] args) {
BinaryTree binaryTree = new BinaryTree();
HeroNode root = new HeroNode(1, "宋江");
HeroNode node2 = new HeroNode(2, "吴用");
HeroNode node3 = new HeroNode(3, "卢俊义");
HeroNode node4 = new HeroNode(4, "林冲");
HeroNode node5 = new HeroNode(5, "关胜");
//先手动创建二叉树
root.setLeft(node2);
root.setRight(node3);
node3.setRight(node4);
node3.setLeft(node5);
binaryTree.setRoot(root);
//测试
System.out.println("前序遍历");//1,2,3,5,4
binaryTree.preOrder();
System.out.println("中序遍历");//2,1,5,3,4
binaryTree.infixOrder();
System.out.println("后续遍历");//2,5,4,3,1
binaryTree.postOrder();
}
}
代码实现
//前序遍历查找
public HeroNode preOrderSearch(int no){
if(this.no == no){
return this;
}
HeroNode resNode = null;
if(this.left != null){
resNode = this.left.preOrderSearch(no);
}
if(resNode != null){
return resNode;
}
if(this.right != null){
resNode = this.right.preOrderSearch(no);
}
return resNode;
}
//中序遍历查找
public HeroNode infixOrderSearch(int no){
HeroNode resNode = null;
if(this.left != null){
resNode = this.left.infixOrderSearch(no);
}
if(resNode != null){//说明找到
return resNode;
}
if(this.no == no){
return this;
}
if(this.right != null){
resNode = this.right.infixOrderSearch(no);
}
return resNode;
}
//后续遍历查找
public HeroNode postOrderSearch(int no){
HeroNode resNode = null;
if(this.left != null){
resNode = this.left.postOrderSearch(no);
}
if(resNode != null){
return resNode;
}
if(this.right != null){
resNode = this.right.postOrderSearch(no);
}
if(this.no == no){
return this;
}
return resNode;
}
//遍历查找
public HeroNode preOrderSearch(int no){
if(root != null){
return root.preOrderSearch(no);
}else {
return null;
}
}
public HeroNode infixOrderSearch(int no){
if(root != null){
return root.infixOrderSearch(no);
}else {
return null;
}
}
public HeroNode postOrderSearch(int no){
if(root != null){
return root.postOrderSearch(no);
}else {
return null;
}
}
System.out.println("前序查找");
HeroNode resNode = binaryTree.preOrderSearch(5);
System.out.println(resNode);
System.out.println("中序查找");
resNode = binaryTree.infixOrderSearch(5);
System.out.println(resNode);
System.out.println("后续查找");
resNode = binaryTree.postOrderSearch(5);
System.out.println(resNode);
要求
思路
代码
//递归删除节点
public void delNode(int no){
if(this.left != null && this.left.no == no){
this.left = null;
return;
}
if(this.right != null && this.right.no == no){
this.right = null;
return;
}
if(this.left != null){
this.left.delNode(no);
}
if(this.left != null){
this.left.delNode(no);
}
if(this.right != null){
this.right.delNode(no);
}
}
//删除节点
public void delNode(int no){
if(root != null){
//如果只有一个root节点
if(root.getNo() == no){
root = null;
}else {
root.delNode(no);
}
}else {
System.out.println("空树,不能删除");
}
}
//测试删除代码
System.out.println("删除前");
binaryTree.preOrder();// 1,2,3,5,4
binaryTree.delNode(5);
System.out.println("删除后");
binaryTree.preOrder();// 1,2,3,4
binaryTree.delNode(3);
binaryTree.preOrder();// 1,2
package tree.binaryTree;
public class BinaryTreeDemo {
public static void main(String[] args) {
BinaryTree binaryTree = new BinaryTree();
HeroNode root = new HeroNode(1, "宋江");
HeroNode node2 = new HeroNode(2, "吴用");
HeroNode node3 = new HeroNode(3, "卢俊义");
HeroNode node4 = new HeroNode(4, "林冲");
HeroNode node5 = new HeroNode(5, "关胜");
//先手动创建二叉树
root.setLeft(node2);
root.setRight(node3);
node3.setRight(node4);
node3.setLeft(node5);
binaryTree.setRoot(root);
//测试 遍历代码
// System.out.println("前序遍历");//1,2,3,5,4
// binaryTree.preOrder();
// System.out.println("中序遍历");//2,1,5,3,4
// binaryTree.infixOrder();
// System.out.println("后续遍历");//2,5,4,3,1
// binaryTree.postOrder();
//测试查找代码
System.out.println("前序查找");
HeroNode resNode = binaryTree.preOrderSearch(5);
System.out.println(resNode);
System.out.println("中序查找");
resNode = binaryTree.infixOrderSearch(5);
System.out.println(resNode);
System.out.println("后续查找");
resNode = binaryTree.postOrderSearch(5);
System.out.println(resNode);
//测试删除代码
System.out.println("删除前");
binaryTree.preOrder();// 1,2,3,5,4
binaryTree.delNode(5);
System.out.println("删除后");
binaryTree.preOrder();// 1,2,3,4
binaryTree.delNode(3);
binaryTree.preOrder();// 1,2
}
}
//定义BinaryTree二叉树
class BinaryTree{
private HeroNode root;
public void setRoot(HeroNode root) {
this.root = root;
}
//删除节点
public void delNode(int no){
if(root != null){
//如果只有一个root节点
if(root.getNo() == no){
root = null;
}else {
root.delNode(no);
}
}else {
System.out.println("空树,不能删除");
}
}
//前序遍历
public void preOrder(){
if(this.root != null){
this.root.preOrder();
}else {
System.out.println("二叉树为空,无法遍历");
}
}
//中序遍历
public void infixOrder(){
if(this.root != null){
this.root.infixOrder();
}else {
System.out.println("二叉树为空,无法遍历");
}
}
//后续遍历
public void postOrder(){
if(this.root != null){
this.root.postOrder();
}else {
System.out.println("二叉树为空,无法遍历");
}
}
//遍历查找
public HeroNode preOrderSearch(int no){
if(root != null){
return root.preOrderSearch(no);
}else {
return null;
}
}
public HeroNode infixOrderSearch(int no){
if(root != null){
return root.infixOrderSearch(no);
}else {
return null;
}
}
public HeroNode postOrderSearch(int no){
if(root != null){
return root.postOrderSearch(no);
}else {
return null;
}
}
}
//创建HeroNode节点
class HeroNode{
private int no;
private String name;
private HeroNode left;
private HeroNode right;
public HeroNode(int no, String name) {
this.no = no;
this.name = name;
}
//递归删除节点
public void delNode(int no){
if(this.left != null && this.left.no == no){
this.left = null;
return;
}
if(this.right != null && this.right.no == no){
this.right = null;
return;
}
if(this.left != null){
this.left.delNode(no);
}
if(this.left != null){
this.left.delNode(no);
}
if(this.right != null){
this.right.delNode(no);
}
}
//前序遍历查找
public HeroNode preOrderSearch(int no){
if(this.no == no){
return this;
}
HeroNode resNode = null;
if(this.left != null){
resNode = this.left.preOrderSearch(no);
}
if(resNode != null){
return resNode;
}
if(this.right != null){
resNode = this.right.preOrderSearch(no);
}
return resNode;
}
//中序遍历查找
public HeroNode infixOrderSearch(int no){
HeroNode resNode = null;
if(this.left != null){
resNode = this.left.infixOrderSearch(no);
}
if(resNode != null){//说明找到
return resNode;
}
if(this.no == no){
return this;
}
if(this.right != null){
resNode = this.right.infixOrderSearch(no);
}
return resNode;
}
//后续遍历查找
public HeroNode postOrderSearch(int no){
HeroNode resNode = null;
if(this.left != null){
resNode = this.left.postOrderSearch(no);
}
if(resNode != null){
return resNode;
}
if(this.right != null){
resNode = this.right.postOrderSearch(no);
}
if(this.no == no){
return this;
}
return resNode;
}
@Override
public String toString() {
return "HeroNode{" +
"no=" + no +
", name='" + name + '\'' +
'}';
}
//前序遍历
public void preOrder(){
System.out.println(this);
//递归向左子树前序遍历
if(this.left != null){
this.left.preOrder();
}
//递归向右子树前序遍历
if(this.right != null){
this.right.preOrder();
}
}
//中序遍历
public void infixOrder(){
if(this.left != null){
this.left.infixOrder();
}
System.out.println(this);
if(this.right != null){
this.right.infixOrder();
}
}
//后续遍历
public void postOrder(){
if(this.left != null){
this.left.infixOrder();
}
if(this.right != null){
this.right.infixOrder();
}
System.out.println(this);
}
public int getNo() {
return no;
}
public void setNo(int no) {
this.no = no;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public HeroNode getLeft() {
return left;
}
public void setLeft(HeroNode left) {
this.left = left;
}
public HeroNode getRight() {
return right;
}
public void setRight(HeroNode right) {
this.right = right;
}
}
基本说明
要求
特点
代码实现
//编写一个 ArrayBinaryTree 实现顺序存储二叉树遍历
class ArrayBinaryTree{
private int[] arr; //存储数据节点的数组
public ArrayBinaryTree(int[] arr){
this.arr = arr;
}
//编写一个方法,完成顺序存储二叉树的前序遍历
public void preOrder(int index){
if(arr == null || arr.length == 0){
System.out.println("数组为空,不能按照二叉树的前序遍历");
}
//输出当前这个元素
System.out.print(arr[index]+" ");
//向左递归遍历
if((index*2+1) < arr.length){
preOrder(2*index + 1);
}
//向右递归遍历
if((index*2 + 2) < arr.length){
preOrder(2*index+2);
}
}
//重载一下前序遍历
public void preOrder(){
this.preOrder(0);
}
}
//中序遍历
public void infixOrder(int index){
if(arr == null || arr.length == 0){
System.out.println("数组为空,不能按照二叉树的前序遍历");
}
//向左递归遍历
if((index*2+1) < arr.length){
infixOrder(index*2+1);
}
//输出当前元素
System.out.print(arr[index]+ " ");
//向右递归遍历
if((index*2+2) < arr.length){
infixOrder(index*2+2);
}
}
public void infixOrder(){
this.infixOrder(0);
}
//后序遍历
public void postOrder(int index){
if(arr == null || arr.length == 0){
System.out.println("数组为空,不能按照二叉树的前序遍历");
}
//向左递归遍历
if((index*2+1) < arr.length){
postOrder(index*2+1);
}
//向右递归遍历
if((index*2+2) < arr.length){
postOrder(index*2+2);
}
//输出当前元素
System.out.print(arr[index]+ " ");
}
public void postOrder(){
this.postOrder(0);
}
public class ArrayBinaryTreeDemo {
public static void main(String[] args) {
int[] arr = {1,2,3,4,5,6,7};
ArrayBinaryTree arrayBinaryTree = new ArrayBinaryTree(arr);
//测试前序遍历,理论结果是 1,2,4,5,3,6,7
arrayBinaryTree.preOrder();
System.out.println();
//中序遍历,理论结果 4,2,5,1,6,3,7
arrayBinaryTree.infixOrder();
System.out.println();
//后序遍历,理论结果 4,5,2,6,7,3,1
arrayBinaryTree.postOrder();
}
}
package tree.arrayBinaryTree;
public class ArrayBinaryTreeDemo {
public static void main(String[] args) {
int[] arr = {1,2,3,4,5,6,7};
ArrayBinaryTree arrayBinaryTree = new ArrayBinaryTree(arr);
//测试前序遍历,理论结果是 1,2,4,5,3,6,7
arrayBinaryTree.preOrder();
System.out.println();
//中序遍历,理论结果 4,2,5,1,6,3,7
arrayBinaryTree.infixOrder();
System.out.println();
//后序遍历,理论结果 4,5,2,6,7,3,1
arrayBinaryTree.postOrder();
}
}
//编写一个 ArrayBinaryTree 实现顺序存储二叉树遍历
class ArrayBinaryTree{
private int[] arr; //存储数据节点的数组
public ArrayBinaryTree(int[] arr){
this.arr = arr;
}
//编写一个方法,完成顺序存储二叉树的前序遍历
public void preOrder(int index){
if(arr == null || arr.length == 0){
System.out.println("数组为空,不能按照二叉树的前序遍历");
}
//输出当前这个元素
System.out.print(arr[index]+" ");
//向左递归遍历
if((index*2+1) < arr.length){
preOrder(2*index + 1);
}
//向右递归遍历
if((index*2 + 2) < arr.length){
preOrder(2*index+2);
}
}
//重载一下前序遍历
public void preOrder(){
this.preOrder(0);
}
//中序遍历
public void infixOrder(int index){
if(arr == null || arr.length == 0){
System.out.println("数组为空,不能按照二叉树的前序遍历");
}
//向左递归遍历
if((index*2+1) < arr.length){
infixOrder(index*2+1);
}
//输出当前元素
System.out.print(arr[index]+ " ");
//向右递归遍历
if((index*2+2) < arr.length){
infixOrder(index*2+2);
}
}
public void infixOrder(){
this.infixOrder(0);
}
//后序遍历
public void postOrder(int index){
if(arr == null || arr.length == 0){
System.out.println("数组为空,不能按照二叉树的前序遍历");
}
//向左递归遍历
if((index*2+1) < arr.length){
postOrder(index*2+1);
}
//向右递归遍历
if((index*2+2) < arr.length){
postOrder(index*2+2);
}
//输出当前元素
System.out.print(arr[index]+ " ");
}
public void postOrder(){
this.postOrder(0);
}
}