Leetcode - 819. Most Common Word

Algorithms, Arrays, Strings

Wow it’s been a while sonce I wrote anything here. I have been doing a lot of functional reactive programming at work and have been wondering how I can apply these new concepts to Leetcode problems. Here is my attempt at finding the most common word from a paragraph that is NOT in the list of banned words.

Leetcode - 10. Regular Expression Matching

Algorithms, Recursion

I’ve seen this problem more than a year ago and back then I kinda memorized the solution.

Leetcode - 11. Container With Most Water

Algorithms, Array

Think of the numbers in the array representing a height. Now, you can create an imaginary box by selecting any two numbers in the array. The max height of water that this imaginary box can hold is the minimuj of the two numbers. So what is the area of the water that can be held?

Leetcode - 23. Merge k Sorted Lists

Algorithms, Linked Lists, Priority Queue

My confusion with these kinds of problems is whether or not a whole new Linked List must be created.

Building a TabBarView with SwiftUI

Open Source, Swift

In my last post I talked about how and why I used Google Sheets as the backend and database for the Aspire Budget apps. When I wrote that post, I had just launched version 1.0 of the app which has received some great response. However, if you did download the app, you would notice that the user interface of the app is really not appealing.

Google Sheets as a Database: Introducing the Aspire Budgeting app

Open Source, Swift

Yeah you heard that right! Who in their right mind would think of using Google Sheets as a database for their app?

Get Random Node from Binary Search Tree

Algorithms, Binary Search Tree

Problem Statement

The goal of this challenge is to build your own BinarySearchTree class which in addition to supporting insert, find and delete also supports a special operation getRandomNode() which returns a random node from the binary search tree with special consideration that each node in the binary search tree is equally likely to be selected.

Check if a Tree is a sub tree of another

Algorithms, Tree, Graph, DFS

Problem Statement

There exists two very large binary trees, with one tree, T1 relatively much bigger than the other T2. How can we efficiently determine if T2 is a sub tree of T1?

Weaving two arrays

Algorithms, Backtracking, Recursion

This is an interesting recursion problem where the aim is to find all the possible weaves of 2 arrays keeping the relative order of the elements the same.

Understanding the fork() system call in UNIX

C++, Unix

The idea of the fork() system call is very beautifully described in the paper “The UNIX Time-Sharing System” by Dennis Ritchie himself and Ken Thompson during their days at Bell Laboratories.

Taming Open Source Swift (SR-7292)

Open Source, Swift

In December 2015, Apple made Swift an open source language and made it available on Github. This piqued my interest, I dug around the code base for a little, cloned it and felt like I had achieved something great. Fast forward to Spring 2017, I made my first contribution to the swift-corelibs-foundation, two contributions to be precise. The way I made these contributions was by digging around the code base for the NSString class and implementing methods marked as NSUnimplemented(). With two accepted PRs to swift-corelibs-foundation, the next thing I did was opened up my resume and under the Key Projects section, added a new bullet point right on top – Currently contribute to Apple’s open source Swift project on Github.

Leetcode - 270. Closest Binary Search Tree Value

Algorithms, Binary Search Tree, Leetcode

If the type of the target and the type of the value in the tree nodes were the same, and the problem was to find the node in the tree that is just smaller than the target, the problem becomes fairly simple. For example, given target = 17 and the graph:

Leetcode - 64. Minimum Path Sum

Algorithms, Array, Dynamic Programming

Problem Statement

Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.

Leetcode - 212. Word Search II

Algorithms, Backtracking, Trie

Problem Statement

Given a 2D board and a list of words from the dictionary, find all words in the board.

Leetcode - 79. Word Search

Algorithms, Array, Backtracking, Depth First Search

Problem Statement

Given a 2D board and a word, find if the word exists in the grid.

Leetcode - 863. All Nodes Distance K In Binary Tree

Algorithms, Binary Tree, Breadth First Search, Depth First Search

Problem Statement

Given the root node of a Binary Tree, a target node and a distance k, return a list of all nodes that are a distance k from the target.

Leetcode - 33. Search In Rotated Sorted Array

Algorithms, Array, Binary Search

This is straight up Binary Search problem with some modifications. When we find the mid point of the given array, one of two things will hold true:

Leetcode - 42. Trapping Rain Water

Algorithms, Array, Recursion, Two Pointers, Leetcode

There’s one thing common between this problem and the Container With Most Water problem and that is the height of the shorter tower dictates the result. In this problem, the amount of water that can accumulate between two towers is limited by the height of the shorter tower. Consider an array [4, 5, 9, 7 ,1, 0 ,4, 0 ,8 ,6 ,5 ,2 ,3] which is represented as:

Generate Parantheses

Algorithms, Backtracking, Recursion, String, Leetcode

Before we start solving this problem, let’s do some math first. The problem statement clearly states that we have N pairs of parentheses to work with. That means for a string to be considered as part of the solution, it must be of size 2N.