Given a binary tree, return the preorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3}, return [1,2,3]. Note: Recursive solution is trivial, could you do it iteratively? 先序遍历应该是三种遍历方式中最好使用非递归来实现的了. 能够每次訪问一个节点后再将其右子节点入栈,然后左子…

Given a binary tree, return the preorder traversal of its nodes' values. Example: Input: [1,null,2,3] 1 \ 2 / 3 Output: [1,2,3] Follow up: Recursive solution is trivial, could you do it iteratively? 给定一个二叉树,返回它的 前序 遍历. 示例: 输入: [1,null,2,3] 1 \ 2 / 3…

题目: Given a binary tree, return the preorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [1,2,3]. Note: Recursive solution is trivial, could you do it iteratively? 解题思路: 利用栈实现,很简单的一题,不多说了,直接上代码 实现代码: #in…

/** * Definition for a binary tree node. * public class TreeNode { * public int val; * public TreeNode left; * public TreeNode right; * public TreeNode(int x) { val = x; } * } */ public class Solution { Stack<int> S = new Stack<int>(); private…

这是一道将二叉树先序遍历,题目不难. 首先采用深搜递归 /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public static List<Integer> resultlist = new A…

给定一个二叉树,返回它的 前序 遍历. 示例: 输入: [1,null,2,3] 1 \ 2 / 3 输出: [1,2,3] 进阶: 递归算法很简单,你可以通过迭代算法完成吗? 递归: class Solution { public: vector<int> res; vector<int> preorderTraversal(TreeNode* root) { GetAns(root); return res; } void GetAns(TreeNode* root) { if…

题目描述 找出给出的字符串S中最长的回文子串.假设S的最大长度为1000,并且只存在唯一解. Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring. 示例1 输入 复制 "abcba" 输出 复制…

给定一个二叉树,返回它的 前序 遍历. 示例: 输入: [1,null,2,3] 1 \ 2 / 3 输出: [1,2,3] 进阶: 递归算法很简单,你可以通过迭代算法完成吗? /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL)…

本文用递归算法实现二叉树的前序.中序和后序遍历,提供Java版的基本模板,在模板上稍作修改,即可解决LeetCode144. Binary Tree Preorder Traversal(二叉树前序遍历),94. Binary Tree Inorder Traversal(二叉树中序遍历),145. Binary Tree Postorder Traversal(二叉树后序遍历). 基本概念 二叉树的遍历是根据访问结点操作发生位置命名: 前序:访问根结点的操作发生在遍历其左右子树之前. 中序:访…

144. 二叉树的前序遍历 144. Binary Tree Preorder Traversal 题目描述 给定一个二叉树,返回它的 前序 遍历. LeetCode144. Binary Tree Preorder Traversal 示例: 输入: [1,null,2,3] 1 \ 2 / 3 输出: [1,2,3] 进阶: 递归算法很简单,你可以通过迭代算法完成吗? Java 实现 Iterative Solution import java.util.LinkedList; import…