From 2ca2d974a079e3d62da38169d8af6af33f45ab27 Mon Sep 17 00:00:00 2001 From: June McEnroe Date: Tue, 20 Dec 2016 20:16:07 -0500 Subject: Day 19 --- src/bin/day19.rs | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 src/bin/day19.rs (limited to 'src') diff --git a/src/bin/day19.rs b/src/bin/day19.rs new file mode 100644 index 0000000..89013b3 --- /dev/null +++ b/src/bin/day19.rs @@ -0,0 +1,37 @@ +use std::io::{self, Read}; + +#[derive(Clone, Copy)] +struct Elf { + gifts: usize, + next: usize, +} + +fn solve(count: usize) -> usize { + let mut circle: Vec = (0..count).map(|i| Elf { gifts: 1, next: i + 1 }).collect(); + circle.last_mut().unwrap().next = 0; + + let mut index = 0; + + while circle[index].gifts < count { + let next = circle[index].next; + circle[index].gifts += circle[next].gifts; + circle[next].gifts = 0; + circle[index].next = circle[next].next; + + index = circle[index].next; + } + + index + 1 +} + +fn main() { + let mut input = String::new(); + io::stdin().read_to_string(&mut input).unwrap(); + + println!("Part 1: {}", solve(input.trim().parse().unwrap())); +} + +#[test] +fn part1() { + assert_eq!(3, solve(5)); +} -- cgit 1.4.1