二叉树删除节点

二叉树删除节点

完成删除结点的操作
规定：①如果删除的结点是叶子结点，则删除该结点
   ②如果删除的结点是非叶子结点，则删除该子树
思路：
1.考虑如果树是空树root,如果只有一个root结点，则等价将二叉树置空。
2.因为二叉树数单向的，所以判断当前结点的子结点是否需要删除结点，而不能去判断当前结点是不是需要删除的结点。
3.如果当前结点的左子结点不为空，并且左子结点就是要删除的结点，就将this.left = null;并且就返回(结束递归删除)
4.如果当前结点的右子结点不为空，并且右子结点就是要删除的结点，就将this.right = null;并且就返回(结束递归删除)
5.如果第3步和第4步没有删除的结点，那么就需要向左子树进行递归删除
6.如果第5步也没有删除的结点，则应当向右子树进行递归删除

public class BinaryTreeDemo {
    public static void main(String[] args) {
        BinaryTree binaryTree = new BinaryTree();
        HeroNode root = new HeroNode(1,"宋江");
        HeroNode node1 = new HeroNode(2,"吴用");
        HeroNode node2 = new HeroNode(3,"卢俊义");
        HeroNode node3 = new HeroNode(4,"林冲");
        HeroNode node4 = new HeroNode(5,"关胜");
        root.setLeft(node1);
        root.setRight(node2);
        node2.setRight(node3);
        node2.setLeft(node4);
        binaryTree.setRoot(root);
        System.out.println("结点删除前的二叉树");
        binaryTree.preOrder();
        binaryTree.delNode(5);
        System.out.println("结点删除后的二叉树");
        binaryTree.preOrder();
    }
}
class BinaryTree{
    HeroNode root;
    public void setRoot(HeroNode root){
        this.root = root;
    }
    public void preOrder(){
        if (this.root != null){
            this.root.preOrder();
        }else{
            System.out.println("当前二叉树为空，无法遍历");
        }
    }
    public void delNode(int no){
        if (root != null){
            if(root.getNo() == no){
                root = null;
            }else{
                root.delNode(no);
            }
        }else{
            System.out.println("该二叉树为空，无法删除");
        }
    }
}

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;
    }

    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 + '\'' +
                '}';
    }

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

    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.right != null){
             this.right.delNode(no);
         }
    }
}

结果如下：

若要删除的结点是非叶子结点，现在不将非叶子结点为根结点的子树删除，而是做如下操作：
如果要删除的结点有一个子结点，则将该子结点替代为删除结点，如果要删除的结点既有左结点又有右结点，则将左结点替代为要删除的结点。

关键代码如下：

 public void delNode(int no){
        if (this.left != null && this.left.no == no){
            if (this.left.left != null && this.left.right == null){
                this.left = this.left.left;
                return;
            }
            if (this.left.right != null && this.left.left == null){
                this.left = this.left.right;
                return;
            }
            if (this.left.left != null &&this.left.right != null){
                HeroNode thisRight = this.left.right;
                this.left = this.left.left;
                this.left.right = thisRight;
                return;
            }
            this.left = null;
            return;
        }
        if (this.right != null && this.right.no == no){
            if (this.right.left != null && this.right.right == null){
                this.right = this.right.left;
                return;
            }
            if (this.right.right != null && this.right.left == null){
                this.right = this.right.right;
                return;
            }
            if (this.right.left != null &&this.right.right != null){
                HeroNode thisRight = this.right.right;
                this.right = this.right.left;
                this.right.right = thisRight;
                return;
            }
            this.right = null;
            return;
        }
        if (this.left != null){
            this.left.delNode(no);
        }
         if (this.right != null){
             this.right.delNode(no);
         }
    }

结果如下：

可能有错误或者实现的很麻烦，希望大佬指正