让我们逆中序遍历一下
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode() {} * TreeNode(int val) { this.val = val; } * TreeNode(int val, TreeNode left, TreeNode right) { * this.val = val; * this.left = left; * this.right = right; * } * } */ class Solution { int pre=0; public TreeNode convertBST(TreeNode root) { dfs(root); return root; } //这里我们逆中序遍历一下 void dfs(TreeNode root){ if(root==null){ return; } dfs(root.right); root.val+=pre; pre=root.val; dfs(root.left); } }