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  • 94. 二叉树的中序遍历-中等难度

    问题描述

    给定一个二叉树,返回它的中序 遍历。

    示例:

    输入: [1,null,2,3]
    1

    2
    /
    3

    输出: [1,3,2]
    进阶: 递归算法很简单,你可以通过迭代算法完成吗?

    来源:力扣(LeetCode)
    链接:https://leetcode-cn.com/problems/binary-tree-inorder-traversal

    解答

    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */
     //迭代没想到,先用递归。
    /*
    这是更简单的迭代
        public void inorder(TreeNode root){
            if(root == null)return;
            inorder(root.left);
            list.add(root);
            inorder(root.right);
        }
    */

    //下面是正解
    class Solution { public List<Integer> list1; public List<Integer> dfs(TreeNode root){ if(root.left == null && root.right == null){ List<Integer> temp1 = new ArrayList<Integer>(); temp1.add(root.val); return temp1; } List<Integer> left = new ArrayList<Integer>(); List<Integer> right = new ArrayList<Integer>(); if(root.left!=null)left = dfs(root.left); if(root.right!=null)right = dfs(root.right); List<Integer> center = new ArrayList<Integer>(); center.add(root.val); left.addAll(center); left.addAll(right); return left; } public List<Integer> inorderTraversal(TreeNode root) { if(root==null)return new ArrayList<Integer>(); list1 = dfs(root); return list1; } }
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  • 原文地址:https://www.cnblogs.com/xxxxxiaochuan/p/13289876.html
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