八、二叉树（基础）

1、二叉树

 

 

 

 

 

二叉树的遍历：

 

 代码实现：

 

package com.treedemo;

public class BinaryTree {

}

//定义二叉树类
class BinaryTreeDemo {
    private Node root;

    public void setRoot(Node root) {
        this.root = root;
    }

    //前序遍历
    public void preOrder() {
        if (this.root != null) {
            this.root.postOrder();
        } 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");
        }
    }

    //后序遍历
    public void postOrder() {
        if (this.root != null) {
            this.root.postOrder();
        } else {
            System.out.println("二叉树为空，无法遍历");
        }
    }

    //前序遍历查找
    public Node preOrderSearch(int no) {
        if (this.root != null) {
            return this.root.preOrderSearch(no);
        } else {
            return null;
        }
    }

    //中序遍历查找
    public Node infixOrderSearch(int no) {
        if (this.root != null) {
            return this.root.infixOrderSearch(no);
        } else {
            return null;
        }
    }

    //后序遍历查找
    public Node postOrderSearch(int no) {
        if (this.root != null) {
            return this.root.postOrderSearch(no);
        } else {
            return null;
        }
    }

    //删除节点
    public void delNode(int no) {
        if (root != null) {
            if (root.no == no) {
                root = null;
            } else {
                root.delNode(no);
            }
        } else {
            System.out.println("空数，不能删除");
        }
    }

}

class Node {
    public int no;
    public String name;
    public Node left;
    public Node right;

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

    @Override
    public String toString() {
        return "Node{" +
                "no=" + no +
                ", name='" + name + '\'' +
                '}';
    }

    //前序遍历
    public void preOrder() {
        System.out.println(this);
        if (this.left != null) {
            this.left.preOrder();
        }
        if (this.right != null) {
            this.right.preOrder();
        }
    }

    //中序遍历
    public void infixOrder() {
        if (this.left != null) {
            this.infixOrder();
        }
        System.out.println(this);
        if (this.right != null) {
            this.right.infixOrder();
        }
    }

    //后序遍历
    public void postOrder() {
        if (this.left != null) {
            this.left.postOrder();
        }
        if (this.right != null) {
            this.right.postOrder();
        }
        System.out.println(this);
    }

    //前序遍历查找
    public Node preOrderSearch(int no) {
        if (this.no == no) {
            return this;
        }
        Node resNode = null;//临时变量，保存找到的node
        //递归查找左节点
        if (this.left != null) {
            resNode = this.left.preOrderSearch(no);
        }
        if (resNode != null) {
            return resNode;
        }
        //递归查找右节点
        if (this.right != null) {
            resNode = this.right.preOrderSearch(no);
        }
        return resNode;
    }

    //中序遍历查找
    public Node infixOrderSearch(int no) {
        Node resNode = null;
        if (this.left != null) {
            resNode = this.left.infixOrderSearch(no);
        }
        if (resNode != null) {
            return resNode;
        }
        if (this.no == no) {
            return this;
        }
        if (this.right != null) {
            resNode = this.right.infixOrderSearch(no);
        }
        return resNode;
    }

    //后序遍历查找
    public Node postOrderSearch(int no) {
        Node 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 (resNode != null) {
            return resNode;
        }
        if (this.no == no) {
            return this;
        }
        return resNode;
    }
    //删除节点

    /**
     * 如果删除的是叶子节点，则删除该节点
     * 如果删除的是非叶子节点，则删除该子数
     *
     * @param no
     */
    public void delNode(int no) {
        //当前节点的左节点不为空，且就是要删除的节点，this.left= null
        if (this.left != null && this.left.no == no) {
            this.left = null;
            return;
        }
        //当前节点的右节点不为空，且就是要删除的节点，this.right= null
        if (this.right != null && this.right.no == no) {
            this.right = null;
            return;
        }
        //向左递归删除
        if (this.left != null) {
            this.left.delNode(no);
        }
        if (this.right != null) {
            this.right.delNode(no);
        }
    }
}