The first question of LeetCode brushing questions, the use of the sum of two numbers and the hash table
Topic description
Given an integer array nums and a target value target, please find the two integers in the array whose sum is the target value, and return their array indices.
You can assume that there will only be one answer for each input ...

Posted by 8ta8ta on Tue, 24 May 2022 17:54:50 +0300

1, Topic analysis
(1) The problem can be abstracted as detecting whether a directed graph has a ring. If yes, return False; If not, return True.
(2) For a directed graph, we can delete nodes with zero penetration one by one. For each deleted node, the connected directed line segment will also be deleted (i.e. the penetration of this point as ...

Posted by judgy on Tue, 24 May 2022 11:48:30 +0300

Leetcode79 medium\color{#FF4500}{medium}medium
Click to enter the original question link: Word Search
Related topics: word search II word search II
[tag] backtracking search, C++ ASCII
subject
Discription
Given a 2D board and a word, find if the word exists in the grid.
The word can be constructed from letters of sequentially adjacent cell ...

Posted by snaack on Tue, 24 May 2022 01:57:25 +0300

Encryption algorithms can be divided into reversible encryption and irreversible encryption, and reversible encryption can be divided into symmetric encryption and asymmetric encryption.
1, Irreversible encryption
Common irreversible encryption algorithms include MD5, HMAC, SHA1, SHA-224, SHA-256, SHA-384, and SHA-512. Among them, SHA-224, SHA- ...

Posted by Fearless_Fish on Tue, 24 May 2022 01:49:38 +0300

Non subject class Xiaobai, record the learning process
The first reaction to this question is dfs, which is easy to record the number of layers, but dfs has defects. See details for details
"Why not use DFS" https://blog.csdn.net/sharemon/article/details/102857989 .
Such as data (1)
8 8
1 3
1 2
2 3
3 4
4 5
5 6
6 7
7 8
...

Posted by aaronlzw_21 on Tue, 24 May 2022 01:28:07 +0300

Decrypt QQ number - queue
The new semester begins. Xiaoha is xiaohum's new deskmate (xiaoha is a little beauty). Xiaohum asks xiaoha about the QQ number. Of course, xiaoha won't tell xiaohum directly. You know the reason. So xiaoha gave xiaohum a string of encrypted numbers, and xiaoha also told xiaohum the decryption rules. The rule is as f ...

Posted by srikanthiv on Mon, 23 May 2022 14:04:57 +0300

1. Sequence zigzag traversal of binary tree
Given a binary tree, return the zigzag hierarchical traversal of its node value. (that is, traverse the next layer from left to right, and then from right to left, and so on, alternating between layers).
For example:
Given binary tree [3,9,20,null,null,15,7],
3
/ \
9 20
/ \
15 7
T ...

Posted by rdoylelmt on Mon, 23 May 2022 10:16:49 +0300

Analysis and java implementation of search related topics in binary tree in Leetcode
In fact, there are some miscellaneous problems in this category. It is basically to find some or a specific value in the binary tree. There are many problems. We will summarize them through two or three articles, but generally speaking, it is basically BFS, whi ...

Posted by HavokDelta6 on Mon, 23 May 2022 10:13:08 +0300

Leetcode Best Time to Buy and Sell Stock series topic analysis and java implementation
The title of this series is to allow us to trade according to restrictions in a continuous period of stock prices to maximize profits. Each derivative title will set some restrictions
Best Time to Buy and Sell Stock I
Best Time to Buy and Sell Stock II
Best ...

Posted by Karlos2394 on Sun, 22 May 2022 21:32:50 +0300

Common dynamic programming problems (2)
This article is reproduced at GitHub address: https://github.com/CyC2018/CS-Notes/ , only for personal review in the future. Integrated various data, invasion and deletion.
Citation analysis:
Content from official account article: https://mp.weixin.qq.com/s/lKQI0aS1MBwfPujC-m_zkA
Use the dynamic ...

Posted by h123z on Sun, 22 May 2022 21:13:49 +0300