成都最好的设计院_创业网站建设规划书_seo怎么做优化排名_网站优化方式有哪些

解法一：执行一次先序遍历，把元素放入list中，然后放回root中

/*** 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 {List<TreeNode> list = new ArrayList<>();public void flatten(TreeNode root) {// 执行一次先序遍历，把元素放入list中,然后放回root中preorder(root);TreeNode pre = root;for(int i=1;i<list.size();i++){pre.right = list.get(i);pre.left = null;pre = pre.right;}}public void preorder(TreeNode root){if(root==null){return;}list.add(root);preorder(root.left);preorder(root.right);}
}