题解 | #牛群的树形结构展开II#

题目考察的知识点 : 二叉树遍历

题目解答方法的文字分析：

构建虚拟头节点和指向当前节点的指针cur

中序遍历二叉树,创建节点temp,在将cur.right指向temp

递归遍历即可

本题解析所用的编程语言: java

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    TreeNode head = new TreeNode(-1);
    TreeNode cur = head;
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return TreeNode类
     */
    public TreeNode flattenII (TreeNode root) {
        // write code here
        if(root == null) return root;
        
        flattenII(root.left);
        TreeNode temp = new TreeNode(root.val);
        cur.right = temp;
        cur = cur.right;
        flattenII(root.right);
        return head.right;
    }
}