public class Solution { TreeNode head = null; TreeNode realHead = null; public TreeNode Convert(TreeNode root) { if(root == null) return null; if(root.left != null) Convert(root.left); if(head == null){ head = root; realHead = root; }else{ head.right = root; root.left = head; head = root; } Convert(root.right); return realHead; } }这个思路清晰好多,网上其他的看的我有点混乱。。。