Advent of Code 2023 - Day 24
I placed 81st on part 1; 99th on part 2; still 5th overall.
I looked up the formula for line-line intersection in part 1. Then I forgot to check if the intersection point is in the future for both hailstones.
I don't really know how to solve part 2. We have a system with n+6 unknowns (our starting position, our velocity, and the time of each intersection) and 3*n equations (at the time of each intersection, our x y z coordinates must match that hailstone). I just plugged it into Z3, which apparently can solve it. Go Z3! (I also tried sympy, but that failed).
Problem: https://adventofcode.com/2023/day/24
Solution: https://github.com/jonathanpaulson/Ad...