Module mbryant_aoc2021::day17

Leans on triangle numbers to reduce the need to brute-force.

Functions

generator

Strip the garbage off the front, then split into two ranges and parse them.

part1

Probe trajectory is a parabola, so it’ll always pass back through 0 with -initial velocity. Assume we’re hitting the lowest part of our target in a single step from 0, then figure out how high it must’ve been. The trajectory will be y + (y-1) + ... = \sum_1^y y, or y * (y+1) / 2.

part2

Brute force the smallest set of possibilities we reasonably can.