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leetcode DFS+BFS+DSU question brushing summary 2 1-symmetric binary tree Title Link: Link here!!! Idea 1: iterative method For a binary tree, the left and right subtrees enter the queue respectively. If the left and right subtrees are empty, the traversal ends. If only one of the left and right subtrees is empty, or the root nodes of the left ...

1, Title Requirements Give you the root node of a binary tree, root, and judge whether it is an effective binary search tree.A valid binary search tree is defined as follows: The left subtree of a node contains only the number less than the current node. The right subtree of a node only contains a number greater than the current node. ...

1, Title Requirements A robot is located in the upper left corner of an m x n grid (the starting point is marked as "Start" in the figure below). The robot can only move down or right one step at a time. The robot tries to reach the lower right corner of the grid (marked as "Finish" in the figure below). How many different ...

Author: Xiao Fu Ge Blog: https://bugstack.cn Precipitate, share and grow, so that you and others can gain something! 😄 Catalogue of Spring hand roll column Chapter 1: Opening introduction, I'm going to take you to Spring! Chapter 2: Small test ox knife, to achieve a simple Bean container Chapter 3: First show your skill and use desig ...

summary Violent recursion is an attempt (local attempt)The problem is transformed into a sub problem of the same kind of problem with reduced scaleSpecify the condition for the end of recursion (base case)After getting the results of the subproblem, there is a decision-making processDo not record the solution of each sub problem, try the m ...

Title Description A path is defined as a sequence that starts from any node in the tree and connects along the parent node to the child node to reach any node. The same node can appear at most in a path sequence. Therefore, the path contains at least one node and does not necessarily pass through the root node. Path sum is the sum of the ...

Title Description Given a tree, preorder and inorder are traversed sequentially. Please construct a binary tree and return its root node. Example 1 Input: preorder = [3,9,20,15,7], inorder=[9,3,15,20,7] output:[3,9,20,null,null,15,7] Example 2 Input: preorder=[-1], inorder=[-1] output: [-1] Tips ...

This article continues to talk about the recursive routine of binary trees.1, Determine whether the binary tree is a search binary treeSearch binary tree definition: for any subtree with X as the head in a binary tree, the left subtree is smaller than X and the right subtree is larger than x. (the classic search binary tree has no duplicate val ...

Add two numbers Give you two non empty linked lists to represent two non negative integers. They store each number in reverse order, and each node can store only one number. Please add the two numbers and return a linked list representing sum in the same form. You can assume that neither number starts with 0 except the number 0. Example 1: Inp ...

0. Preface The brushing algorithm clocked in for the sixth day and today picked up a moderate problem. But with the precipitation knowledge of the previous problem solving, it doesn't feel too painful to solve today. But there is something new to settle, so this is a record. That's how the brushing algorithm works. It's okay in general ...