Find the sum of all left leaves in a given binary tree. Example:     3    / \   9  20     /  \    15   7   There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. 思路:还是递归.仔细看代码,体会递归的设计方法.…

Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. 题目标签:Tree 这道题目给了我们一个二叉树,让我们找到所有左子叶之和.这里需要另外一个function - sumLeftLeaves 还要一…

Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. /** * Definition for a binary tree node. * public class TreeNode { * int…

题目: Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. 分析: 给定一颗二叉树,求左叶子节点的和. 重点在于如何判断左叶子节点,如果一个节点的left存在,且left的left和right都为空…

弄个flag记录是不是左节点就行 int res = 0; public int sumOfLeftLeaves(TreeNode root) { if (root==null) return res; leftSum(root,false); return res; } private void leftSum(TreeNode root,boolean flag) { if (root.left==null&&root.right==null&&flag) res+=r…

404. Sum of Left Leaves [题目]中文版  英文版 /** * 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 { public: int sumOfLeftLea…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目大意 题目大意 解题方法 递归 迭代 日期 [LeetCode] 题目地址:https://leetcode.com/problems/sum-of-left-leaves/ Difficulty: Easy 题目大意 Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \…

Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. # Definition for a binary tree node. # class TreeNode(object): # def __in…

------------------------------------------------------------------- 分两种情况: 1.当前节点拥有左孩子并且左孩子是叶子节点:左孩子值+右孩子子树遍历统计2.不符合上面那种情况的从当前节点劈开为两颗子树分别统计相加即可 AC代码: /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * Tre…

Find the sum of all left leaves in a given binary tree. 左树的值(9+15=24) /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { publi…

［抄题］: Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. [暴力解法]: 时间分析: 空间分析: ［奇葩输出条件］: ［奇葩corner case］: ［思维问题］: root.left ro…

Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. Solution 1:BFS /** * Definition for a binary tree node. * public class Tr…

求所有左节点的和. /** * 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 { public: int sumOfLeftLeaves(TreeNode* root) { if(ro…

404. 左叶子之和 404. Sum of Left Leaves LeetCode404. Sum of Left Leaves 题目描述 计算给定二叉树的所有左叶子之和. 示例: 3 / \ 9 20 / \ 15 7 在这个二叉树中,有两个左叶子,分别是 9 和 15,所以返回 24. Java 实现 TreeNode 结构 class TreeNode { int val; TreeNode left; TreeNode right; TreeNode(int x) { val = x…

404. Sum of Left Leaves Easy Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. package leetcode.easy; /** * Definition for…

LeetCode:Path Sum 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 / \ \…

剑指offer 65. 不用加减乘除做加法(Leetcode 371. Sum of Two Integers) https://leetcode.com/problems/sum-of-two-integers/ 题目: 写一个函数,求两个整数之和,要求在函数体内不得使用加减乘除这四个符号. 分析: 对于不能使用正常的四则运算符,一般就是使用位运算了.而本题要想实现加法,只能使用异或了. 需要注意的是,加法的时候涉及进位,而进位的实现利用与运算. 此外,进位之后还有可能产生进位,所以要在循环里…

Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. 这道题让我们求一棵二叉树的所有左子叶的和,那么看到这道题我们知道这肯定是考二叉树的遍历问题,那么最简洁的写法肯定是用递归,由于我们只需要累加左子叶…

原题链接在这里:https://leetcode.com/problems/sum-of-left-leaves/ 题目: Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. 题解: DFS, 若r…

这是悦乐书的第217次更新,第230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85题(顺位题号是404).找到给定二叉树中所有左叶的总和.例如: 二叉树中有两个左叶,分别为9和15. 返回24. 3 / \ 9 20 / \ 15 7 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win7 64位系统,使用Java语言编写和测试. 02 第一种解法 使用递归. 特殊情况:当root为null时,直接返回0. 正常情况:定义一个变量su…

问题 该文章的最新版本已迁移至个人博客[比特飞],单击链接 https://www.byteflying.com/archives/4084 访问. 计算给定二叉树的所有左叶子之和. 3      / \    9  20   /       \ 15       7 在这个二叉树中,有两个左叶子,分别是 9 和 15,所以返回 24 Find the sum of all left leaves in a given binary tree. 3      / \    9  20   /  …

#-*- coding: UTF-8 -*- # Definition for a binary tree node.# class TreeNode(object):#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneclass Solution(object):        def dfs(self,root,isLeft):      …

1.题目描述 2.问题分析 对于每个节点,如果其左子节点是叶子,则加上它的值,如果不是,递归,再对右子节点递归即可. 3.代码 int sumOfLeftLeaves(TreeNode* root) { if (root == NULL) ; ; if (root->left != NULL) { if (root->left->left == NULL && root->left->right == NULL) ans += root->left-&g…

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, 2…

Given a non-empty 2D matrix matrix and an integer k, find the max sum of a rectangle in the matrix such that its sum is no larger than k. Example: Given matrix = [ [1, 0, 1], [0, -2, 3] ] k = 2 The answer is 2. Because the sum of rectangle [[0, 1], […

If the depth of a tree is smaller than 5, then this tree can be represented by a list of three-digits integers. For each integer in this list: The hundreds digit represents the depth D of this node, 1 <= D <= 4. The tens digit represents the positio…

Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. 计算给定二叉树的所有左叶子之和. 示例: 3 / \ 9 20 / \ 15 7 在这个二叉树中,有两个左叶子,分别是 9 和 15,所以返回 2…

原题链接在这里:https://leetcode.com/problems/path-sum-iv/description/ 题目: If the depth of a tree is smaller than 5, then this tree can be represented by a list of three-digits integers. For each integer in this list: The hundreds digit represents the depth …

LeetCode刷题记录 传送门 Description An undirected, connected treewith N nodes labelled 0...N-1 and N-1 edges are given. The ith edge connects nodes edges[i][0] and edges[i][1] together. Return a list ans, where ans[i] is the sum of the distances between nod…

You are given a binary tree in which each node contains an integer value. Find the number of paths that sum to a given value. The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to…