Skerritt.blog

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141. Linked List Cycle

❤️ I love the algorithm used here! Problem Given head, the head of a linked list, determine if the linked list has a cycle in it. There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the

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235. Lowest Common Ancestor of a Binary Search Tree

Problem Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in the BST. 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

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104. Maximum Depth of Binary Tree

Submission Given the root of a binary tree, return its maximum depth. A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node. Example 1: Input: root = [3,9,20,null,null,15,7] Output: 3 Example

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110. Balanced Binary Tree

Problem Given a binary tree, determine if it is height-balanced. Example 1: Input: root = [3,9,20,null,null,15,7] Output: true Example 2: Input: root = [1,2,2,3,3,null,null,4,4] Output: false Example 3: Input: root = [] Output: true Solution # Definition for a binary tree

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232. Implement Queue using Stacks

Problem Implement a first in first out (FIFO) queue using only two stacks. The implemented queue should support all the functions of a normal queue (push, peek, pop, and empty). Implement the MyQueue class: * void push(int x) Pushes element x to the back of the queue. * int pop() Removes

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704. Binary Search

Problem Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1. You must write an algorithm with O(log n) runtime complexity. Example 1: Input: nums

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242. Valid Anagram

Problem Given two strings s and t, return true if t is an anagram of s, and false otherwise. An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once. Example 1: Input: s = "anagram"

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226. Invert Binary Tree

❤️ This is one of my favourite leetcode problems. I was in a 1v1 race against someone and I came up with the solution without knowing how to do it, I felt so estatic when my code worked first time! Problem Given the root of a binary tree, invert the tree,

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121. Best Time to Buy and Sell Stock

Problem You are given an array prices where prices[i] is the price of a given stock on the ith day. You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock. Return the

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125. Valid Palindrome

Problem A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers. Given a string s, return true if it is a palindrome, or false otherwise. Example 1: Input:

Ares

Introducing Ares - The Fastest Way to Decode Anything

Or how rewriting a popular Python CLI tool in Rust increased our performance by 8445% GitHub - bee-san/Ares: Automated decoding of encrypted text without knowing the key or ciphers usedAutomated decoding of encrypted text without knowing the key or ciphers used - GitHub - bee-san/Ares: Automated decoding of

Functions cheat sheet

I suggest making your own flashcards to study, but if you don’t want to you can use my flashcard deck here. https://quizlet.com/gb/240513173/functions-flash-cards/ A function is just like a function in programming. It takes an input, performs some maths on it, and then outputs the

Mathematical Relations

“Relationships suck” — Everyone at some point in their life What is a relation? There is a relation between two things if there is some connection between them. Relations exist on Facebook, for example. In this blog post we’ll be studying relations between sets. Believe it or not, but relations

An Introduction to Combinatorics

Please consider the following problems: * How many possible sudoku puzzles are there? * Do 37 Londoners exist with the same number of hairs on their head? * In a lottery where 6 balls are selected from 49, how often do two winning balls have consecutive numbers? * In how many ways can we

An Introduction to Probability & Statistics

“Probability Theory Should Be Thrown Under A Bus” — Artifical Intelligence Expert, Carlos E. Perez. We start off by studying Probability Theory and then delve into statistics. Probability and Statistics are used all the time in Computer Science. Machine learning? It’s probability. Data science? It’s statistics. High Level Probability

Mathematical Logic

Logic has been used for thousands of years, from philosophy to mathematics and now to artificial intelligence. Logic is concerned with the truth and falsity of statements. The logic we will be studying will be answering the question: “when does a statement follow from a set of statements?” Note to

How to write a blog post

How to write a blog post Hi. This is the checklists I use whenever I post a blogpost. Enjoy :) Also, this is my checklist. It contains hints / things I’ll want to do. It’s customised to me. You might see a lot of SEO / Convertkit stuff here. Convertkit is

Bitcoins biggest innovation wasn’t the currency

Decentralising a government controlled object such as currency is so much bigger than you know. Bitcoin made its debut in 2011, but the most important thing about it was the concept. The idea of taking something as tangible and government controlled as currency and turning it into a decentralised, anonymous

What is a decision tree in machine learning?

Decision trees, one of the simplest and yet most useful Machine Learning structures. Decision trees, as the name implies, are trees of decisions. Taken from here You have a question, usually a yes or no (binary; 2 options) question with two branches (yes and no) leading out of the tree.

Humanity is dying, we need to save the bees

“The bee is more honored than other animals, not because she labors, but because she labors for others.” — St. John Chrysostom. A third of our crops rely on pollination from bees, 75% of fruit and vegetables need bees to pollinate them. If suddenly a third of our crops and 75%

A guide to altcoins

There are many Alternate (Alt) coins on the market, but what makes them so different? Why would people invest in them instead of Bitcoin? This article seeks to explain Altcoins. Note: This article is not a primer on Bitcoin and presumes you have fundamental knowledge of cryptocurrencies. If not, please

These books will change your life

Note: these links are affiliate links. If you buy through these links I will get a small portion of the profit at no extra cost to you. 1. How to Win Friends and Influence People If you talk to other humans, if you interact with humans, you must read this

Edition 2

Hello 👋 here. 🌊 Welcome to the second edition of 🔮Technologically Clairvoyant🔮 We now have a website! You can view past editions of this newsletter here: https://Technologicallyclairvoyant.com (Github) Without further ado, let’s get into it 🎪 Near Future 🚀 NASA Has Autonomous Robots On The ISS NASA’s first robot, Bumble,

Edition 3

Hello 👋 here. 🌊 Welcome to the third edition of 🔮Technologically Clairvoyant🔮 No announcements this week, so let’s get right into it 🎪 Near Future 🚅 Netherlands’s Rail System Uses WiFi Tracking Following on from last week, the Netherlands publicly admits to using WiFi tracking. However, unlike TFL, they detail more on

Edition 4

Hello 👋 here. Welcome to Edition 4 🔮 Near Future 🗽 New York Tenants Fight As Landlords Embrace Facial Recognition Cameras In a bid to stop facial recongition replacing traditional keys, 130 tenants have signed a petition. The public sector heavily regulates facial recognition, but there are currently no laws in the private