From aef4230b15b5459f98e30f102fe9ac62f78f0b48 Mon Sep 17 00:00:00 2001 From: June McEnroe Date: Sun, 24 Dec 2017 10:59:42 -0500 Subject: Day 15 --- 2017/src/bin/day15.rs | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) create mode 100644 2017/src/bin/day15.rs (limited to '2017/src/bin') diff --git a/2017/src/bin/day15.rs b/2017/src/bin/day15.rs new file mode 100644 index 0000000..dbf041a --- /dev/null +++ b/2017/src/bin/day15.rs @@ -0,0 +1,49 @@ +use std::io::{self, Read}; + +struct GenA(u64); + +impl Iterator for GenA { + type Item = u64; + + fn next(&mut self) -> Option { + self.0 = self.0.wrapping_mul(16807) % 2147483647; + Some(self.0) + } +} + +struct GenB(u64); + +impl Iterator for GenB { + type Item = u64; + + fn next(&mut self) -> Option { + self.0 = self.0.wrapping_mul(48271) % 2147483647; + Some(self.0) + } +} + +fn judge(a: u64, b: u64) -> usize { + GenA(a).zip(GenB(b)) + .take(40_000_000) + .filter(|&(a, b)| a & 0xFFFF == b & 0xFFFF) + .count() +} + +fn solve1(input: &str) -> usize { + let mut iter = input.split_whitespace(); + let a = iter.clone().nth(4).unwrap().parse().unwrap(); + let b = iter.nth(9).unwrap().parse().unwrap(); + judge(a, b) +} + +fn main() { + let mut input = String::new(); + io::stdin().read_to_string(&mut input).unwrap(); + + println!("Part 1: {}", solve1(input.trim())); +} + +#[test] +fn part1() { + assert_eq!(588, judge(65, 8921)); +} -- cgit 1.4.1