神仙题.为啥我第一眼看上去以为是个普及题 路径有两种,第一种是从 LCA 一边下去的,第二种是从 LCA 两边都下去了的. 先考虑第一种. 先枚举路径长度 \(h\). 当 LCA 编号是 \(x\) 时,且所有儿子都是往左走时,和为 \((2^h-1)x\):所有儿子都往右走时,和为 \((2^h-1)x+2^h-1\).显然 \((2^h-1)x\le s\le (2^h-1)x+2^h-1\). 考虑从下往上第 \(i\) 个点从左儿子变成右儿子时(其它不变),总和会增加 \(2^i-1\…

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"] 题目标签:Tree 这道题目给了我们一个二叉树,让我们记录所有的路径,返回一个array string list. 我们可以另外设一…

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"] 简单的遍历查找路径问题,代码如下: /** * Definition for a binary tree node. * struc…

Given a binary tree, return all root-to-leaf paths. Note: A leaf is a node with no children. Example: Input: 1 / \ 2 3 \ 5 Output: ["1->2->5", "1->3"] Explanation: All root-to-leaf paths are: 1->2->5, 1->3 /** * Defin…

题意: 给出一个二叉树,输出根到所有叶子节点的路径. 思路: 直接DFS一次,只需要判断是否到达了叶子,是就收集答案. /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { v…

目录 简单的 组合的 题目链接 简单的 设从节点\(x\)开始不断往左儿子走h-1步,则编号和为\(x\sum_{i=0}^{h-1}2^i=x(2^h-1)\). 若倒数第\(i\)步走向的是右儿子,则编号和会增加\(\sum_{j=0}^{i-1}2^j=2^i-1\). 这样,从\(x\)往下走形成的长为\(h\)的链中,其中倒数\(i,i\in T\)步时走向右儿子,倒数\(i,i\not\in T\)步走向左儿子,这样得到的编号和为 \[ x(2^h-1)+\sum_{i\in T}2…

Binary Tree Restoring Time Limit: 1 Second      Memory Limit: 65536 KB      Special Judge Given two depth-first-search (DFS) sequences of a binary tree, can you find a binary tree which satisfies both of the DFS sequences? Recall that a binary tree i…

Binary Tree Traversals Time Limit: 1000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 2681    Accepted Submission(s): 1178 Problem Description A binary tree is a finite set of vertices that is either empty or…

这是悦乐书的第199次更新,第206篇原创 01 看题和准备 今天介绍的是LeetCode算法题中Easy级别的第62题(顺位题号是257).给定二叉树,返回所有根到叶路径.例如: 输入: 1 / \ 2 3 \ 5 输出:["1-> 2-> 5","1-> 3"] 说明:所有根到叶路径是:1-> 2-> 5, 1-> 3 注意:叶子是没有子节点的节点. 本次解题使用的开发工具是eclipse,jdk使用的版本是1.8,环境是wi…

描述 Given an N×N grid of fields (1≤N≤500), each labeled with a letter in the alphabet. For example: ABCD BXZXCDXBWCBA Each day, Susa walks from the upper-left field to the lower-right field, each step taking her either one field to the right or one fi…