给定一个二叉树,以集合方式返回其中序/先序方式遍历的所有元素. 有两种方法,一种是经典的中序/先序方式的经典递归方式,另一种可以结合栈来实现非递归 Given a binary tree, return the inorder traversal of its nodes' values. For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [1,3,2]. OJ's Binary Tree Serialization: The s…

题目描述: 给定一颗二叉树,使用非递归方法实现二叉树的中序遍历 题目来源: http://oj.leetcode.com/problems/binary-tree-inorder-traversal/ 题目分析: 递归到非递归的转换.使用栈描述递归的调用过程,while循环体计算递归程序的计算部分.因为每次while循环只能处理一次递归调用,使用标记记录栈中节点的计算痕迹,例如:用tag记录当前根的调用记录,当根的左右子树均未调用时,令tag值为0,当根的左子树已经调用过时,令tag值为1. 时…

We run a preorder depth first search on the rootof a binary tree. At each node in this traversal, we output D dashes (where D is the depth of this node), then we output the value of this node.  (If the depth of a node is D, the depth of its immediate…

Given a binary tree, return the inorder, preorder, postorder traversal of its nodes' values. Example: Input: [1,null,2,3] 1 \ 2 / 3 inorder Output: [1,3,2] preorder Output: [1,2,3] postorder Output: [3,2,1] 这三个题目的思路及总结都在LeetCode questions conlusion_I…

Tree Traversals Again Tree Traversals Again 这里的第一个tip就是注意到非递归中序遍历的过程中,进栈的顺序恰好是前序遍历的顺序,而出栈的顺序恰好是中序遍历的顺序. 第二个需要注意的就是如何根据中序遍历和前序遍历构建出一棵二叉树. 第三个是二叉树的后序遍历,这里我采用的是后序遍历的方法 import java.util.Scanner; import java.util.Stack; /** * @Author WaleGarrett * @Date 2…

Given preorder and inorder traversal of a tree, construct the binary tree. Note:You may assume that duplicates do not exist in the tree. For example, given preorder = [3,9,20,15,7] inorder = [9,3,15,20,7] Return the following binary tree: 3 / \ 9 20…

题目来源: https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/ 题意分析: 根据二叉树的中序和前序遍历结果,反推这个树,假设只有一个这样的树. 题目思路: 前序遍历的第一个树将中序遍历分成两半,左半部分是左子树,右半部分是右子树,递归重构这棵树. 代码(python): # Definition for a binary tree node. # class TreeNo…

Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level). For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7 return its level order traversal as: [ [3], [9,20], [15,7] ] 层序…

Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level). For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7 return its level order traversal as: [ [3], [9,20], [15,7] ] 层序…

Given preorder and inorder traversal of a tree, construct the binary tree. Note:You may assume that duplicates do not exist in the tree. 这道题要求用先序和中序遍历来建立二叉树,跟之前那道Construct Binary Tree from Inorder and Postorder Traversal 由中序和后序遍历建立二叉树原理基本相同,针对这道题,由于先…