Algorithm Explained: Get the max items you can purchase with a fixed budget

Problem statement: Given a fixed budget and a list of item prices. What is the max number of items you can purchase? You can only buy each item once. Note: This is the Mark and Toys problem from HackerRank. Example: You’re given $10 and a list of items to choose from: A cool coffee cup … Read more

Algorithm Explained: Sum two big integers the hard way

Problem statement: Sum two big integers that are passed in as strings. Return the sum as a string. In other words, implement the following method: Constraint: Don’t use the built-in BigInteger class (note: this is the name in C# and may have a different name in other languages). Do it the hard way instead. If … Read more

Solving whiteboard problems to prepare for coding interviews

Companies like to ask you to solve whiteboard problems during coding interviews. If it’s an in-person interview, they’ll ask you to solve the problem on a physical whiteboard. If it’s a remote interview, they’ll either have you solve the problem on a website like HackerRank, or they’ll ask you the question in a “digital whiteboard” … Read more

Multithreaded quicksort in C#

One day I decided to challenge myself by trying to implement multithreaded quicksort. I wanted to see how it would compare to the built-in sort function – Array.Sort(). I came up with two algorithms that were 2-4x faster than Array.Sort(): Top-down: divide-fork-sort-merge Bottom-up: quicksort with fork-on-recursion After continuing to tinker, in attempts to further optimize, … Read more