题目 Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example: Given the below binary tree and sum = 22, 分析 本题目与上一题LeetCode(112) Path Sum虽然类型相同,但是需要在以前的基础上,多做处理一些: 与Path Sum相比,本题是求出路径,所以,在找到满足的路…

题目 Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example: Given the below binary tree and sum = 22, return true, as there exist a root-to-leaf…

题目 Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T. Each number in C may only be used once in the combination. Note: All numbers (including target) will be p…

首先要说明二叉树的问题就是用递归来做,基本没有其他方法,因为这数据结构基本只能用递归遍历,不要把事情想复杂了. #112 Path Sum 原题链接:https://leetcode.com/problems/path-sum/ . 判断从树的根节点到叶子节点的路径中,是否有一条所有节点上的值之和和特定的数字,即sum. 从根节点到叶子节点,线路的起点的是固定的,只需要不断递归下去,判断在叶子节点处是否满足根节点加到该节点的值之和为sum. 这个限制条件把这个问题简化了很多很多. /** * D…

Medium! 题目描述: 给定一个可能包含重复元素的整数数组 nums,返回该数组所有可能的子集(幂集). 说明:解集不能包含重复的子集. 示例: 输入: [1,2,2] 输出: [ [2], [1], [1,2,2], [2,2], [1,2], [] ] 解题思路: 这道子集合之二是之前那道Subsets 子集合 的延伸,这次输入数组允许有重复项,其他条件都不变,只需要在之前那道题解法的基础上稍加改动便可以做出来,我们先来看非递归解法,拿题目中的例子[1 2 2]来分析,根据之前Subse…

题目 Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and j is at most k. 分析 题目描述:给定一个整数序列,查找是否存在两个下标分别为i和j的元素值nums[i]=nums[j]且满足i…

Medium! 题目描述: 给定一个二叉树和一个目标和,找到所有从根节点到叶子节点路径总和等于给定目标和的路径. 说明: 叶子节点是指没有子节点的节点. 示例:给定如下二叉树,以及目标和 sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1 返回: [ [5,4,11,2], [5,8,4,5] ] 解题思路: 这道二叉树路径之和在之前的基础上又需要找出路径,但是基本思想都一样,还是需要用深度优先搜索DFS,只不过数据结构相对复杂一点,需要用到二维的…

题目 Given an array of integers, every element appears three times except for one. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? 分析 由上一题改动而来,LeetCode 136 Single Nu…

题目 Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. The update(i, val) function modifies nums by updating the element at index i to val. Example: Given nums = [1, 3, 5] sumRange(0, 2) -> 9 update(1…

题目 Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2). Range Sum Query 2D The above rectangle (with the red border) is defined by (row1, col1)…

题目 Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. Example: Given nums = [-2, 0, 3, -5, 2, -1] sumRange(0, 2) -> 1 sumRange(2, 5) -> -1 sumRange(0, 5) -> -3 Note: You may assume that the array…

题目: Given an array of integers, find two numbers such that they add up to a specific target number. The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note t…

题目 Given an array of non-negative integers, you are initially positioned at the first index of the array. Each element in the array represents your maximum jump length at that position. Your goal is to reach the last index in the minimum number of ju…

Medium! 题目描述: 给定一个可包含重复数字的序列,返回所有不重复的全排列. 示例: 输入: [1,1,2] 输出: [ [1,1,2], [1,2,1], [2,1,1] ] 解题思路: 这道题是之前那道Permutations 全排列的延伸,由于输入数组有可能出现重复数字,如果按照之前的算法运算,会有重复排列产生,我们要避免重复的产生,在递归函数中要判断前面一个数和当前的数是否相等,如果相等,前面的数必须已经使用了,即对应的visited中的值为1,当前的数字才能使用,否则需要跳过,这…

题目 Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T. The same repeated number may be chosen from C unlimited number of times. Note: All numbers (including target) wi…

题目 Follow up for "Unique Paths": Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 and 0 respectively in the grid. For example, There is one obstacle in the mi…

题目 Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example, Given n = 3, You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ] 分析 与54题Spiral Matrix相似题,为一个二维矩阵进行螺旋状赋值 AC代码…

题目 Given an array of integers, find out whether there are two distinct indices i and j in the array such that the difference between nums[i] and nums[j] is at most t and the difference between i and j is at most k. 分析 题目描述:给定一个整数序列,查找是否存在两个下标分别为i和j的元…

[LeetCode]113. Path Sum II 解题报告(Python) 标签(空格分隔): LeetCode 作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.me/ 题目地址:https://leetcode.com/problems/path-sum-ii/description/ 题目描述: Given a binary tree and a sum, find all root-to-leaf paths where each…

LeetCode 二叉树路径问题 Path SUM(①②③)总结 Path Sum II leetcode java 描述 Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example:Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \…

Leetcode之动态规划(DP)专题-931. 下降路径最小和(Minimum Falling Path Sum) 给定一个方形整数数组 A,我们想要得到通过 A 的下降路径的最小和. 下降路径可以从第一行中的任何元素开始,并从每一行中选择一个元素.在下一行选择的元素和当前行所选元素最多相隔一列. 示例: 输入:[[1,2,3],[4,5,6],[7,8,9]] 输出:12 解释: 可能的下降路径有: [1,4,7], [1,4,8], [1,5,7], [1,5,8], [1,5,9] [2…

题目链接:Path Sum II | LeetCode OJ Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example: Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1 return [ [5,4,11,2],…

112. Path Sum 自己的一个错误写法: class Solution { public: bool hasPathSum(TreeNode* root, int sum) { if(root == NULL) return false; ; return hasPathSum(root,sum,value); } bool hasPathSum(TreeNode* root,int sum,int value){ if(root == NULL){ if(value == sum) r…

Problem 1 [Balanced Binary Tree] Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1. Pr…

Path Sum II Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example:Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1 return [ [5,4,11,2], [5,8,4,5] ] 这题是在Path…

Path Sum 题目链接 题目要求: Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example: Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 /…

题目 Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy one and sell one share of the stock multiple times).…

目录 题目链接 注意点 解法 小结 题目链接 Path Sum II - LeetCode 注意点 不要访问空结点 解法 解法一:递归,DFS.每当DFS搜索到新节点时,都要保存该节点.而且每当找出一条路径之后,都将这个保存为一维vector的路径保存到最终结果二维vector中.并且,每当DFS搜索到子节点,发现不是路径和时,返回上一个结点时,需要把该节点从一维vector中移除. /** * Definition for a binary tree node. * struct TreeNo…

思路: 简单搜索 总结: dfs 框架 1. 需要打印路径. 在 dfs 函数中假如 vector 变量, 不用 & 修饰的话就不需要 undo 2. 不需要打印路径, 可设置全局变量 ans, 在 dfs 函数中对 ans 判定, 判定的位置尽可能的多 3. 对 tree 遍历, 有两种办法, 第一种是 if(root == NULL) 第二种是 if(root->left == NULL), 我一般用第二种, 效率比较高, 但是在第二种 return 1, 第一种 return 0 4.…

Path Sum II 题解 原创文章,拒绝转载 题目来源:https://leetcode.com/problems/path-sum-ii/description/ Description Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. Example Given the below binary tree and sum = 22 5…