1.前中后序查找思路分析

1.1前序查找

- 判斷與當(dāng)前節(jié)點(diǎn)是否相等，如果相等則返回當(dāng)前節(jié)點(diǎn)，否則判斷當(dāng)前節(jié)點(diǎn)的左子節(jié)點(diǎn)是否為空
- 如果左子節(jié)點(diǎn)不為空徘铝，則遞歸前序查找左子樹南用，找到就返回節(jié)點(diǎn)，否則就繼續(xù)判斷當(dāng)前節(jié)點(diǎn)右子節(jié)點(diǎn)是否為空
- 如果右子節(jié)點(diǎn)不為空仿野，則遞歸前序查找右子樹，找到就返回節(jié)點(diǎn)，否則返回null

//前序查找
    public HeroNode preIndexSearch(int no){
        //判斷與當(dāng)前節(jié)點(diǎn)no是否相同典尾，相同返回
        if(this.no==no){
            return this;
        }
        //判斷左子節(jié)點(diǎn)是否為空，如果不為空糊探，遞歸前序查詢左子樹,如果相等钾埂，返回
        HeroNode temp = null;
        if(this.left!=null){
            temp =  this.left.preIndexSearch(no);
        }
        if(temp!=null){
            return temp;
        }
        if(this.right!=null){
            temp = this.right.preIndexSearch(no);
        }
        return temp;
    }

1.2中序查找

- 判斷當(dāng)前節(jié)點(diǎn)的左子節(jié)點(diǎn)是否為空，如果不為空就遞歸中序查找科平，找到就返回
- 否則與當(dāng)前節(jié)點(diǎn)比較褥紫，如果相等就返回，否則繼續(xù)判斷當(dāng)前節(jié)點(diǎn)的右子節(jié)點(diǎn)是否為空
-如果右子節(jié)點(diǎn)不為空瞪慧，就遞歸中序查找右子樹故源，找到就返回，否則返回null

 //中序查找
    public HeroNode infixIndexSearch(int no){
        HeroNode temp = null;
        if(this.left!=null){
            temp = this.left.infixIndexSearch(no);
        }
        if(temp!=null){
            return temp;
        }
        if (this.no==no){
            return this;
        }
        if(this.right!=null){
            temp = this.right.infixIndexSearch(no);
        }
        return temp;
    }

1.3后序查找

- 判斷當(dāng)前節(jié)點(diǎn)的左子樹是否為空汞贸，如果不為空绳军，則遞歸后序查找左子樹，找到就返回
-否則判斷當(dāng)前節(jié)點(diǎn)的右子節(jié)點(diǎn)是否為空矢腻，如果不為空门驾，則遞歸查找右子樹，找到就返回
- 否則與當(dāng)前節(jié)點(diǎn)比較多柑，相等返回當(dāng)前節(jié)點(diǎn)奶是，否則返回null

//后序查找
    public HeroNode postIndexSearch(int no){
        HeroNode temp = null;
        if(this.left!=null){
            temp = this.left.postIndexSearch(no);
        }
        if(temp!=null){
            return temp;
        }
        if(this.right!=null){
            temp = this.right.postIndexSearch(no);
        }
        if(temp!=null){
            return temp;
        }
        if(this.no==no){
            return this;
        }
        return temp;
    }

2.完整代碼

package com.yc.day06;

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, "吳用");
        HeroNode node3 = new HeroNode(3, "盧俊義");
        HeroNode node4 = new HeroNode(4, "林沖");
        binaryTree.setRoot(root);
        root.setLeft(node2);
        root.setRight(node3);
        node3.setRight(node4);
        System.out.println("前序遍歷：");
        binaryTree.preSort();
        System.out.println("");
        HeroNode heroNode = binaryTree.preIndexSearch(2);
        System.out.println("前序查找結(jié)果："+heroNode);
        HeroNode heroNode1 = binaryTree.infixIndexSearch(2);
        System.out.println("中序查找結(jié)果："+heroNode1);
        HeroNode heroNode2 = binaryTree.postIndexSearch(2);
        System.out.println("后序查找結(jié)果："+heroNode2);
    }
}
//創(chuàng)建二叉樹
class BinaryTree{
    HeroNode root;
    public void setRoot(HeroNode heroNode){
        this.root = heroNode;
    }
    //前序遍歷
    public void preSort(){
        root.preSort();
    }
    //中序遍歷
    public void infixSort(){
        root.infixSort();
    }
    //后序遍歷
    public void postSort(){
        root.postSort();
    }
    //前序查找
    public HeroNode preIndexSearch(int no){
        if(root!=null){
            return root.preIndexSearch(no);
        }
       return null;
    }
    //中序查找
    public HeroNode infixIndexSearch(int no){
        if(root!=null){
            return root.infixIndexSearch(no);
        }
        return null;
    }
    //后序查找
    public HeroNode postIndexSearch(int no){
        if(root!=null) {
            return root.postIndexSearch(no);
        }
        return null;
    }
}
//創(chuàng)建節(jié)點(diǎn)類
class HeroNode{
    private int no;
    private String name;
    private HeroNode left;
    private HeroNode right;

    public HeroNode() {
    }

    public HeroNode(int no, String name) {
        this.no = no;
        this.name = name;
    }

    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;
    }

    @Override
    public String toString() {
        return "HeroNode{" +
                "no=" + no +
                ", name='" + name + '\'' +
                '}';
    }
    //前序遍歷
    public void preSort(){
        System.out.println(this);
        if(this.left!=null){
            this.left.preSort();
        }
        if(this.right!=null){
            this.right.preSort();
        }
    }
    //中序遍歷
    public void infixSort(){
        if(this.left!=null){
            this.left.infixSort();
        }
        System.out.println(this);
        if(this.right!=null){
            this.right.infixSort();
        }
    }
    //后序遍歷
    public void postSort(){
        if(this.left!=null){
            this.left.postSort();
        }
        if(this.right!=null){
            this.right.postSort();
        }
        System.out.println(this);
    }
    //前序查找
    public HeroNode preIndexSearch(int no){
        //判斷與當(dāng)前節(jié)點(diǎn)no是否相同，相同返回
        if(this.no==no){
            return this;
        }
        //判斷左子節(jié)點(diǎn)是否為空，如果不為空聂沙，遞歸前序查詢左子樹,如果相等秆麸，返回
        HeroNode temp = null;
        if(this.left!=null){
            temp =  this.left.preIndexSearch(no);
        }
        if(temp!=null){
            return temp;
        }
        if(this.right!=null){
            temp = this.right.preIndexSearch(no);
        }
        return temp;
    }
    //中序查找
    public HeroNode infixIndexSearch(int no){
        HeroNode temp = null;
        if(this.left!=null){
            temp = this.left.infixIndexSearch(no);
        }
        if(temp!=null){
            return temp;
        }
        if (this.no==no){
            return this;
        }
        if(this.right!=null){
            temp = this.right.infixIndexSearch(no);
        }
        return temp;
    }
    //后序查找
    public HeroNode postIndexSearch(int no){
        HeroNode temp = null;
        if(this.left!=null){
            temp = this.left.postIndexSearch(no);
        }
        if(temp!=null){
            return temp;
        }
        if(this.right!=null){
            temp = this.right.postIndexSearch(no);
        }
        if(temp!=null){
            return temp;
        }
        if(this.no==no){
            return this;
        }
        return temp;
    }
}