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...
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...
Convert Ternary Expression to Binary Tree Bottom View of Binary Tree Ancestors in Binary Tree All Root to Leaf Paths Sum of all numbers formed by root to leaf path Minimum distance between two given nodes of a Binary Tree K-th smallest element in a Binary Search Tree ...
public void flatten(TreeNode root) { if(root==null) return; TreeNode curr = root; while(curr!=null){ //保存右子树, 后面用 TreeNode oldRight = curr.right; //左子树不为空, 执行一系列改变指向的操作 if(curr.left!=null){ //找到左子树的最右节点 TreeNode rightMost = curr.left; while(...
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. ...
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 duplicates. See detailed answers for more analysis and explanation. ...
LeetCode Top 100 Liked Questions 297. Serialize and Deserialize Binary Tree (Java版; Hard) 题目描述 Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, ...