寻找二叉树的前驱后继结点

public class SuccessNode {
    public static class Node{
        public int value;
        public Node left;
        public Node right;
        public Node parent;
        public Node(int data){
            this.value = data;
        }
    }
    // 中序二叉树 前驱后继结点
    //后继结点
    public static Node getPosNode(Node node){
        if(node == null){
            return node;
        }
        if(node.right != null){
            return getLeftMost(node.right);
        }else{
            Node parent = node.parent;
            while(parent != null && node != parent.left){
                node = parent;
                parent = node.parent;
            }
            return parent;
        }
    }
    public static Node getLeftMost(Node node){
        if(node == null){
            return null;
        }
        while(node.left != null){
            node = node.left;
        }
        return node;
    }
    //前驱结点
    public static Node getPreNode(Node node){
        if(node == null){
            return null;
        }
        if(node.left != null){
            return getRightMost(node.left);
        }else{
            Node parent = node.parent;
            while(parent != null && node != parent.right){
                node = parent;
                parent = node.parent;
            }
            return parent;
        }
    }
    public static Node getRightMost(Node node){
        if(node == null){
            return null;
        }
        while(node.right != null){
            node = node.right;
        }
        return node;
    }
    public static void main(String[] args) {
        Node head = new Node(6);
        head.parent = null;
        head.left = new Node(3);
        head.left.parent = head;
        head.left.left = new Node(1);
        head.left.left.parent = head.left;
        head.left.left.right = new Node(2);
        head.left.left.right.parent = head.left.left;
        head.left.right = new Node(4);
        head.left.right.parent = head.left;
        head.left.right.right = new Node(5);
        head.left.right.right.parent = head.left.right;
        head.right = new Node(9);
        head.right.parent = head;
        head.right.left = new Node(8);
        head.right.left.parent = head.right;
        head.right.left.left = new Node(7);
        head.right.left.left.parent = head.right.left;
        head.right.right = new Node(10);
        head.right.right.parent = head.right;

        Node test = head.left.left;
        System.out.println(test.value + " next: " + getPosNode(test).value);
        System.out.println(test.value + " pre: " + getPreNode(test));
        test = head.left.left.right;
        System.out.println(test.value + " next: " + getPosNode(test).value);
        System.out.println(test.value + " pre: " + getPreNode(test).value);
        test = head.left;
        System.out.println(test.value + " next: " + getPosNode(test).value);
        System.out.println(test.value + " pre: " + getPreNode(test).value);
        test = head.left.right;
        System.out.println(test.value + " next: " + getPosNode(test).value);
        System.out.println(test.value + " pre: " + getPreNode(test).value);
        test = head.left.right.right;
        System.out.println(test.value + " next: " + getPosNode(test).value);
        System.out.println(test.value + " pre: " + getPreNode(test).value);
        test = head;
        System.out.println(test.value + " next: " + getPosNode(test).value);
        System.out.println(test.value + " pre: " + getPreNode(test).value);
        test = head.right.left.left;
        System.out.println(test.value + " next: " + getPosNode(test).value);
        System.out.println(test.value + " pre: " + getPreNode(test).value);
        test = head.right.left;
        System.out.println(test.value + " next: " + getPosNode(test).value);
        System.out.println(test.value + " pre: " + getPreNode(test).value);
        test = head.right;
        System.out.println(test.value + " next: " + getPosNode(test).value);
        System.out.println(test.value + " pre: " + getPreNode(test).value);
        test = head.right.right; // 10's next is null
        System.out.println(test.value + " next: " + getPosNode(test));
        System.out.println(test.value + " pre: " + getPreNode(test).value);
    }
}

1 next: 2
1 pre: null
2 next: 3
2 pre: 1
3 next: 4
3 pre: 2
4 next: 5
4 pre: 3
5 next: 6
5 pre: 4
6 next: 7
6 pre: 5
7 next: 8
7 pre: 6
8 next: 9
8 pre: 7
9 next: 10
9 pre: 8
10 next: null
10 pre: 9