https://leetcode.cn/problems/number-of-ways-to-reconstruct-a-tree 这道题曾经在周赛难度分top1呆了几年,如今已经不在难度分top5了。破局的关键是父节点的邻居数肯定不少于子节点,而根节点的邻居数一定是n-1。所以应该先找到根节点,然后逐层向下建树,子节点的邻居一定是父节点的子集,否则就是非法;如果子...
LeetCode Top 100 Liked Questions 105. Construct Binary Tree from Preorder and Inorder Traversal (Java版; Medium) 题目描述 Given preorder and inorder traversal of a tree, construct the binary tree. Note: You may assume that duplicates do not exist in the tree. For example, given preorder ...
Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow...
Blind 75 LeetCode Questions Curated List of Top 75 LeetCode Questions to Save Your Time Blind 75 LeetCode Questions: Ace Algorithms Coding Interview - Udemy course https://www.udemy.com/course/blind-75-leetcode-questions-ace-algorithms-coding-interview/ ...
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. The path does not need to go through the root. ...
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what is the value in the case of HashSet? Well, in the case of HashSet a dummy object is used as a value and key objects are the actual element on Set point of view. Since HashMap doesn't allow duplicate keys it also follows the contract of set data structure to not allow ...
LeetCode Top 100 Liked Questions 98. Validate Binary Search Tree (Java版; Medium) 题目描述 Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than the node's key...