How cp case-insensitivity can cause chaos!

Been doing Advent of Code in the last couple of days. I completed Day 6. I have been doing it from an Xcode project. However I was thinking it would be nice if I could do it from command line. So I started to do some code clean up. First I started with renaming the folder from AOC to aoc. I did: cp -r AOC aoc I saw a new aoc directory created....

December 6, 2022 · 4 min

How to Think Recursively - Part 2

Please read How to Think Recursively before reading this post. This post re-applies the steps mentioned in the previous post on a more challenging question. Question Return all possible ways we can generate a well-formed parenthesis? Examples: if n = 1 then we can only form () if n = 2 then we can form (()) and ()() if n = 3 then we can form ((())), (())(), ()(()), (()()), (), (), () Let’s try applying our 4 steps:...

November 15, 2022 · 4 min

How to Think Recursively - Part 1

These articles are about the gotchas I faced when trying to think recursively. The logic in principle should apply to most recursive problems. In this post, I will use the following question as a point of reference: ‘Count how many ways you can climb a staircase. You can jump either one step at a time or two steps at a time.’ Example if there are 3 stair cases then you can either jump:...

November 15, 2022 · 8 min

Why does pod lib lint suddenly fail to build?

I made some changes to the repo of our private pod. Pushed up my branch. Tests all ran. Then my colleague asked for some updates to my PR (pull request). I made changes and pushed it to GH. I wanted to merge the changes. But then CI was failing. So I ran CI again. It failed again. They say third time is the charm. So I ran it two more times....

October 24, 2022 · 6 min

How Understanding State Machines Helps With Building Trees and Graphs

My team was dealing with a large flow, where user can transition from multiple states or sometimes skip certain states. We didn’t have a centralized controller, every screen just had logic on where it should go next. This made it difficult for us to see all our logic at once. We asked around and was told state machines are a good fit for our situation. State machines are void of any UX....

October 6, 2022 · 7 min
self-contained rv

What Resources Does Apple Provide for teaching iOS to students?

Note: This post has got a bit longer than what I originally intended. You might want to skip to the very end to see the verdict and table first and then read again. I’ve started an iOS training course in my local community. At the beginning I thought it would be easy for me to just start training people with whatever I know. Later I decided to look at some available resources....

September 21, 2022 · 9 min

Longest Increasing Subsequence Length

What’s a subsequence? Any selection of items from the original array. The selection must respect the order. Meaning for [1,2,3,4,5] only two of the four below are subsequences: [1,2,3,4,5] ✅ [1,4,3,2,5] ❌ order not respected [1,2,5] ✅ [5,1] ❌ order not respected What’s the difference between a subsequence and a subarray? Subarray, is just like subsequence, that is order must be respected. Additionally the sub-array has to be made of continuous elements....

August 25, 2022 · 3 min

Which Way Am I Sorting?

I always got confused as to what’s the end result my sort. I wasn’t sure if it would end up being ascending or descending. The ultimate trick is to not think of up vs down. Instead think of increasing/decreasing from left to right. We perceive arrays as horizontal beings. Hence left and right make more sense vs up and down let nums = [1,4,2,3] let sorted_nums = arr.sorted(by: { $0 < $1 // left is smaller [1,2,3,4] i....

August 3, 2022 · 1 min

Recover Binary Tree

Question: You have a binary tree. But only two of its elements have been swapped. This makes it a faulty binary tree. The challenge is to swap those two elements. And fix the tree. Solution I knew I had to traverse it. But then what? With a little help from reading online, I realized I should traverse it, and store the values into an array. Then you just loop the array and find the bad indexes....

June 27, 2022 · 4 min

How to Calculate the Middle Index?

A good number of interview questions require you to constantly split an array/string in half. This is relatively easy to achieve when the array count is odd. However when the count is even, it’s not as easy. let a = [1,3,8,10,22] // middle index is 2 let b = [1,3,8,10] // middle index is 1.5 which is non-existent. So what now? Most important thing to note is: There’s no such thing as “middle index” when the count is even, I mean there’s two middles in that case....

June 19, 2022 · 3 min