Dan's Blog

Fourier Transform https://www.bilibili.com/video/BV1aW4y1y7Hs/?spm_id_from=333.337.search-card.all.click&vd_source=7cf01a4cc731f5d6335bce33c114b60c 在图像处理中，信号指的是图像中的像素值。 在图像处理中，信号频率通常指的是图像中的空间频率。空间频率表示图像中像素值的变化率，即一个图像中不同位置上的像素值如何随空间位置的变化而变化。 低空间频率：低频分量代表图像中较大区域的平滑变化，例如背景或均匀纹理。这些分量对应于图像中的整体趋势。 中等空间频率：中等频率分量代表中等大小的特征和纹理，如一些物体的轮廓或边缘。它们通常对应于物体之间的界限和边界。 高空间频率：高频分量对应于小细节、细小的特征、纹理和边缘。它们表示图像中的急剧变化，通常包含图像的细节信息。 In the spatial frequency domain representation of a Fourier-transformed image, the center ...

Gaussian smoothinghttps://homepages.inf.ed.ac.uk/rbf/HIPR2/gsmooth.htm#:~:text=The%20effect%20of%20Gaussian%20smoothing,order%20to%20be%20accurately%20represented.) The idea of Gaussian smoothing is to use 2-D Gaussian distribution as a `point-spread’ function, and this is achieved by convolution. High/Low pass filter, Fourier transformhttps://www.cnblogs.com/wj-1314/p/11983496.html#:~:text=%E5%82%85%E9%87%8C%E5%8F%B6%E5%8F%98%E6%8D%A2%E5%8F%AF%E4%BB%A5,%E5%A2%9E%E5%BC%BA%E5%92%8C%E9%94 ...

Back Tracking🌼在二叉树系列中，我们已经不止一次，提到了回溯，例如二叉树：以为使用了递归，其实还隐藏着回溯。 回溯是递归的副产品，只要有递归就会有回溯。 回溯法解决的问题回溯法，一般可以解决如下几种问题： 组合问题：N个数里面按一定规则找出k个数的集合 切割问题：一个字符串按一定规则有几种切割方式 子集问题：一个N个数的集合里有多少符合条件的子集 排列问题：N个数按一定规则全排列，有几种排列方式 棋盘问题：N皇后，解数独等等 回溯法模板1234567891011void backtracking(参数) { if (终止条件) { 存放结果; return; } for (选择：本层集合中元素（树中节点孩子的数量就是集合的大小）) { 处理节点; backtracking(路径，选择列表); // 递归 回溯，撤销处理结果 }} 这里给出Carl总结的回溯算法模板。 在讲二叉树的递归中我们说了递 ...

Tree🌼Recursive VS. BackTrack https://blog.csdn.net/ajianyingxiaoqinghan/article/details/79682147 Depth-first traversalThe recursive traversal of a binary treeIn-order traversal (Left-Root-Right): Traverse the left subtree. Visit the current node (Root). Traverse the right subtree. Pre-order traversal (Root-Left-Right): Visit the current node (Root). Traverse the left subtree. Traverse the right subtree. Post-order traversal (Left-Right-Root): Traverse the left subtree. Traverse the right s ...

DP🌼Summarize:What’s DP?You break down the problem into smaller subproblems. The solution to the original problem can then be constructed from the solutions of its subproblems. 重叠子问题 Dynamic Programming Five Steps:Here, we’ll use a one-dimensional DP array to store the results of recursion. Determine the meaning of the DP array and its indices: The meaning of dp[i] is: Establish the recurrence relation: dp[i] = dp[i - 1] + dp[i - 2]. Initialize the DP array: dp[0] = 0; dp[1] &#x ...

AWSdeploy(elastic beanstalk): https://www.freecodecamp.org/news/how-to-use-elastic-beanstalk-to-deploy-node-js-app/ RDS: https://aws.amazon.com/getting-started/hands-on/create-mysql-db/ downald mysql on ec2: https://www.youtube.com/watch?v=0Teg0Kv8Gak https://awswithatiq.com/how-to-install-mysql-on-amazon-linux-2023-fedora-version/ open phpmyadmin on ec2: (didn’t actually do this) https://www.youtube.com/watch?v=HSmu7kmv_ng https://docs.phpmyadmin.net/en/latest/setup.html#manually-creating-the-f ...

note The queue data structure follows the FIFO (First In First Out) principle. A stack follows the LIFO (Last In First Out) principle, i.e., the element inserted at the last is the first element to come out. stack: push pop peek* 12345stack.push(1);stack.push(2);stack.peek(); // 返回 1stack.pop(); // 返回 1stack.isEmpty(); // 返回 false stack.push() stack.peek() 12345678910111213141516171819202122public static void main(String args[]) { // Creating an empty Stack Stack< ...

mongoose encrypt the way that mongoose encrypt works is that it will encrypt when you call save and decrypt when you call find. 123456789101112131415161718192021222324252627282930313233343536373839404142434445const mongoose = require("mongoose");const encrypt = require("mongoose-encryption");const userSchema= new mongoose.Schema({ email: String, password: String}); // no longer a simple Javascript object but it's actually an object that's created fr ...

REACTJSX (JavaScript XML) is an extension to JavaScript syntax used in React. It allows you to write HTML-like code within JavaScript, making it easier to create and manipulate the structure of user interfaces. files got html content in javascript files. JS: 1234567891011121314151617181920212223242526272829// var ReactDOM = require("react-dom"); dotn need to write this anymoreimport React from "react";import ReactDOM from"react-dom";//ReactDOM.render(WHAT TO SHOW, ...

REACTJSX (JavaScript XML) is an extension to JavaScript syntax used in React. It allows you to write HTML-like code within JavaScript, making it easier to create and manipulate the structure of user interfaces. JS: 1234567891011121314151617181920212223import React from "react";import ReactDOM from"react-dom";//ReactDOM.render(WHAT TO SHOW, WHERE TO SHOW)ReactDOM.render(<h1>helloworld</h1>, document.getElementById("root"));// render method can only take ...