二叉树所有节点转换成大于该节点的平均值，没有最大值就转换成0

import java.util.ArrayList;
import java.util.List;
import java.util.function.ToIntFunction;
import java.util.stream.Collectors;

public class Test {
    static class Node implements Cloneable {
        int val;
        Node left;
        Node right;

        public Node(int val, Node left, Node right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }


        @Override
        protected Node clone() throws CloneNotSupportedException {
            Node node = new Node(val, left == null ? null : left.clone(), right == null ? null : right.clone());
            return node;
        }
    }

    /**
     *              3
     *       2             5
     *   1             4       6
     *
     *   转换成
     *              5
     *       4             6
     *   5             5       0
     */
    public static void main(String[] args) throws CloneNotSupportedException {
        Node node1 = new Node(1, null, null);
        Node node2 = new Node(2, node1, null);
        Node node4 = new Node(4, null, null);
        Node node6 = new Node(6, null, null);
        Node node5 = new Node(5, node4, node6);
        Node root = new Node(3, node2, node5);

        updateNode(root.clone(), root);
        System.out.println(root);
    }

    static List<Integer> gtList = new ArrayList();

    public static void updateNode(Node root, Node currentNode) {
        // 终止条件
        if (currentNode == null || root == null) {
            return;
        }
        // 选取大于当前节点的nodes
        getNodesAverage(root, currentNode);
        Double rightAvg = gtList.stream().collect(Collectors.averagingInt(new ToIntFunction<Object>() {
            @Override
            public int applyAsInt(Object value) {
                return (int) value;
            }
        }));
        gtList.clear();
        // updateNodeValue
        updateCurrentNode(currentNode, rightAvg.intValue());
        // 递归节点
        updateNode(root, currentNode.left);
        updateNode(root, currentNode.right);
    }

    /**
     * 重置节点value
     */
    public static void updateCurrentNode(Node currentNode, int newVal) {
        currentNode.val = newVal;
    }


    /**
     * 计算平均值
     */
    public static void getNodesAverage(Node root, Node node) {
        if (node == null || root == null) {
            return;
        }
        if (root.val > node.val) {
            gtList.add(root.val);
        }
        // 递归
        getNodesAverage(root.left, node);
        getNodesAverage(root.right, node);
    }
}