We are given the head node root of a binary tree, where additionally every node's value is either a 0 or a 1. Return the same tree where every subtree (of the given tree) not containing a 1 has been removed. (Recall that the subtree of a node X is X,…

題目是說,如果左右子樹都不存在又自已為0,就去掉那個子樹(設為null) recursive後序,左子樹,右子樹,然後是根 自已同時又是別人的子樹,所以要告訢根自已是不是存在 從a開始,左右子樹都不存在,而自已是1 所以傳回true 告訢 root(c) 左子樹a 不可以刪掉(存在) b,左右子樹都不存在,而自已是0 所以傳回false 告訢 root(c) 右子樹b 可以刪掉(不存在) c,右子樹b可以刪除,把right = null,左子樹不可刪.雖然自已是0,可是左子樹存在所以傳回true…

LeetCode:Binary Tree Level Order Traversal 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 ord…

LeetCode: Binary Tree Traversal 题目:树的先序和后序. 后序地址:https://oj.leetcode.com/problems/binary-tree-postorder-traversal/ 先序地址:https://oj.leetcode.com/problems/binary-tree-preorder-traversal/ 后序算法:利用栈的非递归算法.初始时,先从根节点一直往左走到底,并把相应的元素进栈:在循环里每次都取出栈顶元素,如果该栈顶元素的右…

https://leetcode.com/contest/weekly-contest-79/problems/binary-tree-pruning/ -- 814 from leetcode tree traverse (post traverse) left right and root the model void traverse(node){ if(node.left!=null) traverse(node.left); if(node.right!=null) traverse(…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 后序遍历 日期 题目地址:https://leetcode.com/problems/binary-tree-pruning/description/ 题目描述 We are given the head node root of a binary tree, where additionally every node's value is eith…

dfs 要点是这一句: return node.val==1 or node.left or node.right 完整代码: # Definition for a binary tree node. # class TreeNode: # def __init__(self, x): # self.val = x # self.left = None # self.right = None import functools class Solution: @functools.lru_cach…

Given a binary tree, return the vertical order traversal of its nodes' values. (ie, from top to bottom, column by column). If two nodes are in the same row and column, the order should be from left to right. Examples: Given binary tree [3,9,20,null,n…

Given a binary tree, find the length of the longest consecutive sequence path. The path refers to any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The longest consecutive path need to be from p…

Given a binary tree, return all root-to-leaf paths. For example, given the following binary tree: 1 / \ 2 3 \ 5 All root-to-leaf paths are: ["1->2->5", "1->3"] 这道题给我们一个二叉树,让我们返回所有根到叶节点的路径,跟之前那道Path Sum II 二叉树路径之和之二很类似,比那道稍微简单一…

Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom. For example:Given the following binary tree, 1 <--- / \ 2 3 <--- \ \ 5 4 <--- You should return [1, 3,…

Given a binary tree where all the right nodes are either leaf nodes with a sibling (a left node that shares the same parent node) or empty, flip it upside down and turn it into a tree where the original right nodes turned into left leaf nodes. Return…

Given a binary tree, return the postorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [3,2,1]. Note: Recursive solution is trivial, could you do it iteratively? 经典题目,求二叉树的后序遍历的非递归方法,跟前序,中序,层序一样都需要用到栈,后续的…

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? 一般我们提到树的遍历,最常见的有先序遍历,中序遍历,后序遍历和层序遍历,它们用递归实现起…

Given a binary tree, find the maximum path sum. The path may start and end at any node in the tree. For example:Given the below binary tree, 1 / \ 2 3 Return 6. 这道求二叉树的最大路径和是一道蛮有难度的题,难就难在起始位置和结束位置可以为任意位置,我当然是又不会了,于是上网看看大神们的解法,看了很多人的都没太看明白,最后发现了网友Yu's…

Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root). For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7 return its bottom-up level order tr…

Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between). For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7 return its…

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 inorder traversal of its nodes' values. For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [1,3,2]. Note: Recursive solution is trivial, could you do it iteratively? confused what "{1,#,2,3}" means? > re…

原题链接在这里:https://leetcode.com/problems/binary-tree-vertical-order-traversal/ 题目: Given a binary tree, return the vertical order traversal of its nodes' values. (ie, from top to bottom, column by column). If two nodes are in the same row and column, th…

原题链接在这里:https://leetcode.com/problems/binary-tree-longest-consecutive-sequence/ 题目: Given a binary tree, find the length of the longest consecutive sequence path. The path refers to any sequence of nodes from some starting node to any node in the tre…

原题链接在这里:https://leetcode.com/problems/binary-tree-upside-down/ Given a binary tree where all the right nodes are either leaf nodes with a sibling (a left node that shares the same parent node) or empty, flip it upside down and turn it into a tree whe…

1.题目说明 Given a binary tree, find the maximum path sum.   The path may start and end at any node in the tree.   For example: Given the below binary tree,   1 / \ 2 3 Return 6.   2.解法分析: leetcode中给出的函数头为:int maxPathSum(TreeNode *root) 给定的数据结构为: Definit…

Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root). For example: Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7 return its bottom-up level order t…

Given a binary tree, you need to find the length of Longest Consecutive Path in Binary Tree. Especially, this path can be either increasing or decreasing. For example, [1,2,3,4] and [4,3,2,1] are both considered valid, but the path [1,2,4,3] is not v…

Given a binary tree, return the tilt of the whole tree. The tilt of a tree node is defined as the absolute difference between the sum of all left subtree node values and the sum of all right subtree node values. Null node has tilt 0. The tilt of the …

We are given the head node root of a binary tree, where additionally every node's value is either a 0 or a 1. Return the same tree where every subtree (of the given tree) not containing a 1 has been removed. (Recall that the subtree of a node X is X,…

偶然在面试题里面看到这个题所以就在Leetcode上找了一下,不过Leetcode上的比较简单一点. 题目: Given a binary tree, find the maximum path sum. For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along the parent-child connections. Th…

Given a binary tree, find the maximum path sum. The path may start and end at any node in the tree. For example:Given the below binary tree, 1 / \ 2 3 Return 6. 题目意思很简单,就是给定一棵二叉树,求最大路径和.path 可以从任意 node 开始,到任意 node 结束. 这道题在 LeetCode 上的通过率只有 20% 多一点,并被…

原题地址:https://oj.leetcode.com/problems/binary-tree-maximum-path-sum/ 题意: Given a binary tree, find the maximum path sum. The path may start and end at any node in the tree. For example:Given the below binary tree, 1 / \ 2 3 Return 6. 解题思路:这道题是在树中寻找一条路…