题解 | #牛群的树形结构展开II#

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 {
    /**
     * 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
        TreeNode result = new TreeNode(-1);
        TreeNode temp = result;
        inOrder(root,temp);
        return result.right;
    }

    public TreeNode inOrder(TreeNode node,TreeNode target){
        if(node == null){
            return target;
        }

        target = inOrder(node.left,target);
        target.right = new TreeNode(node.val);
        target = target.right;
        target = inOrder(node.right,target);
        return target;
    }
}