AoC# 2024 - Day 17: Chronospatial Computer

It’s Advent of Code time 🎄

Advent of Code is an Advent calendar of small programming puzzles for a variety of skill levels that can be solved in any programming language you like.

The single-star days continue on Day 17…

Part 1 ⭐️

Very happy with my implementation as it’s clear and readable, making use of a simple Instruction class:

public class Instruction
{
    public int Opcode { get; set; }
    public int Operand { get; set; }
};

And a switch statement on the current Opcode for the Computer’s workings.

Part 2 ❌

I had full-day plans today so my time this morning was limited - I figured that if I could modify the Computer loop in Part1 to return early if it’s not going well then I might be able to brute force an answer¹ if I left it running all day:

do
{
    // Computer implementation here (omitted)

    if (breakEarly && output.Count > 0 && !ProgramInput.StartsWith(string.Join(',', output)))
        return string.Join(',', output);

} while (instructionPointer < Program.Count);

return string.Join(',', output);

… hours later it hadn’t completed so this is demonstrably not the right way to solve this!

---

1. Rarely is brute forcing Part2 possible - Eric Wastl tends to make sure of it 🤓 ↩