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,null,null,15,7], 3 / \ 9 20 / \ 15 7 retur…

103. 二叉树的锯齿形层次遍历 103. Binary Tree Zigzag Level Order Traversal 题目描述 给定一个二叉树,返回其节点值的锯齿形层次遍历.(即先从左往右,再从右往左进行下一层遍历,以此类推,层与层之间交替进行). LeetCode103. Binary Tree Zigzag Level Order Traversal中等 例如: 给定二叉树 [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 返回锯齿形层次遍历如…

与102相比就增加了flag,用以确定要不要进行reverse操作 reverse:STL公共函数,对于一个有序容器的元素reverse ( s.begin(),s.end() )可以使得容器s的元素顺序反转: C++代码: /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x),…

103. 二叉树的锯齿形层次遍历 给定一个二叉树,返回其节点值的锯齿形层次遍历.(即先从左往右,再从右往左进行下一层遍历,以此类推,层与层之间交替进行). 例如: 给定二叉树 [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 返回锯齿形层次遍历如下: [ [3], [20,9], [15,7] ] class Solution { public List<List<Integer>> zigzagLevelOrder(TreeNode roo…

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,null,null,15,7], 3 / \ 9 20 / \ 15 7 retur…

原题地址 基本数据结构操作,二叉树的层次遍历. 代码: vector<vector<int> > zigzagLevelOrder(TreeNode *root) { vector<vector<int> > res; vector<TreeNode *> layer; bool l2r = true; layer.push_back(root); while (!layer.empty()) { vector<TreeNode *>…

此题难度在于如何标记每一层的末尾节点. 思路1:队列层次遍历,遇到偶数层末尾反转一下数组 class Solution { public: vector<vector<int>> zigzagLevelOrder(TreeNode* root) { vector<vector<int>> res; if(!root) return res; int t; vector<int> tmp; deque<TreeNode*> deq; d…

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,null,null,15,7], 3 / \ 9 20 / \ 15 7 retur…

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,null,null,15,7], 3 / \ 9 20 / \ 15 7 retur…

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 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…

原题链接 题目要求以"Z"字型遍历二叉树,并存储在二维数组里. 利用BFS,对每一层进行遍历.对于每一层是从左还是从右,用一个整数型判断当前是偶数行还是奇数行就可以了. class Solution { public: vector<vector<int>> res; vector<vector<int>> zigzagLevelOrder(TreeNode *root) { if (root == NULL) return res; s…

题目链接 : https://leetcode-cn.com/problems/binary-tree-zigzag-level-order-traversal/ 题目描述: 给定一个二叉树,返回其节点值的锯齿形层次遍历.(即先从左往右,再从右往左进行下一层遍历,以此类推,层与层之间交替进行). 例如: 给定二叉树 [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 返回锯齿形层次遍历如下: [ [3], [20,9], [15,7] ] 思路: 上一题一样…

1. 题目 2. 解答 定义两个栈 s_l_r.s_r_l 分别负责从左到右和从右到左遍历某一层的节点,用标志变量 flag 来控制具体情况,根节点所在层 flag=1 表示从左到右遍历,每隔一层改变一次遍历方向. 用栈 s_l_r 从左到右遍历当前层节点时,按照先左子节点再右子节点的顺序将这一层节点的子节点依次放入栈 s_r_l 中. 用栈 s_r_l 从右到左遍历当前层节点时,按照先右子节点再左子节点的顺序将这一层节点的子节点依次放入栈 s_l_r 中. /** * Definition f…

相对于102题,稍微改变下方法就行 迭代方法: 在102题的基础上,加上一个变量来判断是不是需要反转 反转的话,当前list在for循环结束后用collection的反转方法就可以实现反转 递归方法: 由于有层数,所以用层数%2判断是不是需要反转 反转的话就元素都添加到最前边,一层添加完后就是反的 下边是递归方法 List<List<Integer>> res = new ArrayList<>(); public List<List<Integer>…

Note: 后面数字n表明刷的第n + 1遍, 如果题目有**, 表明有待总结 Conclusion questions: [LeetCode] questions conclustion_BFS, DFS LeetCode questions conclustion_Path in Tree [LeetCode] questions conlusion_InOrder, PreOrder, PostOrder traversal [LeetCode] questions for Dynamic…

BFS, DFS 的题目总结. Directed graph: Directed Graph Loop detection and if not have, path to print all path. BFS/DFS: (可以用BFS或者DFS的,主要还是遍历) [LeetCode] 733. Flood Fill_Easy tag: BFS     1 [LeetCode] 690. Employee Importance_Easy tag: BFS    1 [LeetCode] 529…

leetcode探索中级答案汇总: https://leetcode-cn.com/explore/interview/card/top-interview-questions-medium/ 1)数组和字符串: leetcode 15 三数之和(medium)排序+双指针 leetcode73 矩阵置零 (medium) 空间节省技巧 leetcode 49 字母异位词分组(medium)排序+哈希 leetcode 3 无重复字符的最长子串(medium) DP leetcode5 最长回文…

Yet Another Source Code for LintCode Current Status : 232AC / 289ALL in Language C++, Up to date (2016-02-10) For more problems and solutions, you can see my LintCode repository. I'll keep updating for full summary and better solutions. See cnblogs t…

LeetCode:二叉树的锯齿形层次遍历[103] 题目描述 给定一个二叉树,返回其节点值的锯齿形层次遍历.(即先从左往右,再从右往左进行下一层遍历,以此类推,层与层之间交替进行). 例如:给定二叉树 [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 返回锯齿形层次遍历如下: [ [3], [20,9], [15,7] ] 题目分析 层次遍历,应该很容易想到BFS(宽度优先搜索算法),此处是锯齿形,即一层是从左往右,下一层就是从右往左. 解决办法是每一层都…

// 103. Binary Tree Zigzag Level Order Traversal // https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/description/ // swift // Definition for a binary tree node. public class TreeNode { public var val: Int public var left: TreeNo…

题目来源 https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/ 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). 题意分…

一天一道LeetCode 本系列文章已全部上传至我的github,地址:ZeeCoder's Github 欢迎大家关注我的新浪微博,我的新浪微博 欢迎转载,转载请注明出处 (一)题目 来源: https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/ Given a binary tree, return the zigzag level order traversal of its nodes' values…

Medium! 题目描述: 给定一个二叉树,返回其节点值的锯齿形层次遍历.(即先从左往右,再从右往左进行下一层遍历,以此类推,层与层之间交替进行). 例如:给定二叉树 [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 返回锯齿形层次遍历如下: [ [3], [20,9], [15,7] ] 解题思路: 这道二叉树的之字形层序遍历是之前那道[LeetCode] Binary Tree Level Order Traversal 二叉树层序遍历的变形,不同之处…

题目 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}, return its zigzag level ord…

和树有关的题目求深度 -> 可以利用层序遍历 -> 用到层序遍历就想到使用BFS 896. 单调数列 - 水题 class Solution: def isMonotonic(self, A) -> bool: if sorted(A) == A or sorted(A, reverse=True) == A: return True return False 690. 员工的重要性 - 简单BFS class Solution: def getImportance(self, empl…

No.103 ZigzagLevelOrder 二叉树的锯齿形层次遍历 题目 给定一个二叉树,返回其节点值的锯齿形层次遍历.(即先从左往右,再从右往左进行下一层遍历,以此类推,层与层之间交替进行). 示例 给定二叉树 [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 返回锯齿形层次遍历如下: [ [3], [20,9], [15,7] ] 思路 代码 No.104 MaxDepth 二叉树的最大深度 题目 给定一个二叉树,找出其最大深度. 二叉树的深度为根…

102. 二叉树的层次遍历 题目描述 给定一个二叉树,返回其按层次遍历的节点值. (即逐层地,从左到右访问所有节点). 例如: 给定二叉树: [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 返回其层次遍历结果: [ [3], [9,20], [15,7] ] 分析 本题的核心在于如何标记哪一些元素在同一个层次上,该解法使用一个size进行控制 代码 class Solution { public: vector<vector<int>> l…

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,null,null,15,7], 3 / \ 9 20 / \ 15 7 retur…

Binary Tree Zigzag Level Order Traversal 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,#…