Sleeping Forest

Sleeping Forest

Data Structure (8) - Graph

Definition Graph G = (V, E), where V is a set of vertices, and E is a set of edges. For some reason unknown, people usually use n for the number of vertices, and m for the number of edges. |V|=n, |E|=m An edge can not point to nowhere.

Data Structure (7) - Disjoint Sets

Disjoint Sets Disjoint Sets is the data structure that supports the operation of adding one element (as their own set), [finding the label/canonical_name of one element in a set], and union 2 sets. It can represents data like: * Set1 (people whose favorite color's green) * Set2 (people

Data Structure (6) - Heaps & Priority Queues

ADT * insert(value) * remove() * isEmpty() Where value is among int, string, double, char... or objects that supports < operator. Heap Unsorted Array: O(1)* insert, O(n) removeMin (need to find min first) Unsorted Linked List: O(1) insert, O(n) removeMin Sorted Array: O(n)* insert, O(1) removeMin

Regex Cheat Sheet

Syntax Description * 0 or more times + 1 or more times ? 1 or 0 times {m} exactly m times {m,} m or more times {m,n} m to n times (both inclusive) \n new line […] range or character class (e.g. [a-z0-9] all lowercases and digits) [^…] not in range

Data Structure (5) - Hash Table

Hash Table A hash table has: * A hash function h(k) * An array * Something that handles collisions and else Dictionary in Python is a hash table. Hash Function A function that maps keys from key-space to an integer bounded by array size. A hash function consists of 2 parts:

Data Structure (4) - Kd-Tree & B-Tree

Kd-Tree Short for k-dimension-tree. When search is not enough in one dimension, Kd-Trees may be used. e.g. Search in 2D. Given x1, x2, y1, y2, find all points within the range. If we don't want to go through all of the points – O(

Data Structure (3) - BST & AVL Tree

Binary Search Tree A BST (binary search tree) is a tree T such: * T = {} or * T = {r, TL, TR} where all nodes in TL has keys less than r, all nodes in TR has keys greater than r, and TL and TR are BSTs. // BST.h #pragma once template <

Data Structure (2) - Tree & Traversal

Tree A tree is an acyclic graph ( a graph that has no circle in it) Tree ADT ADT: Abstract Data Type * insert: add data (node) to tree * remove: remove data (node) from tree * create: create empty tree * traversal: iterate over data // BinaryTree.h #pragma once template <typename T>

Data Structure (1) - Lists, Stack & Queue

Lists Linked List // List.h #pragma once template <typename T> class List { public: // private: class ListNode { public: T data; // a place to store data ListNode *next; // a pointer pointing to next node ListNode(T &data) : data(data), next(NULL); // a constructor that inits data with ref // and

Notes for C++ (2)

Memory Stack Memory Stack memory is used for function calls. Stack memory starts near top of memory (e.g. 0xffff00f0, starts from ffff something, and not 0000 something) and moves down, automatically managed by systems with function calls. The memory only lasts as long as the function goes. #include Square.

Notes for C++ (1)

Files and Classes Header Header files are used like interfaces in Java: Square.h #pragma once // include guard // to stop circular imports of headers from looping non-stop namespace test123 { class Square { public: Square(); // constructor with no param; default constructor Square(double length); // custom constructor // Square(const Square &s)

Nginx - make proxy_pass work with URI

nginx workaround: I wanna use proxy_pass with URI!

PM2 cheat sheet

PM2 cheat sheet (site/app management) (auto restart on server boot)

Installing PostgreSQL on VPS (Ubuntu 20.04 LTS)

Notes for how to install a specific version of PostgreSQL. Installation ref: https://www.postgresql.org/download/linux/ubuntu/ * To use the PostgreSQL Apt Repository # Create the file repository configuration: sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main"

Testing

Testing unsplash plugin. Test img from other sources (if CSP's working ok): Testing markdown: h1 h2 h3 h4 * line 1 * sub 1 * sub 2 * sub - sub 1. mix 2. mix * line 2 * line 3 1. line 1 2. line 2 3. (2.1 seems not working) 3. line