Day 4

src/day4.rs

@@ -0,0 +1,69 @@
+use crate::util::prelude::*;
+
+static INPUT: &str = include_str!("inputs/day4.txt");
+
+fn parse_range(s: &str) -> core::ops::RangeInclusive<uint> {
+	let mut parts = s.split('-');
+	let lo = parts.next().unwrap();
+	let hi = parts.next().unwrap();
+
+	let lo = lo.parse().unwrap();
+	let hi = hi.parse().unwrap();
+
+	lo..=hi
+}
+
+fn fully_contains<U: PartialOrd>(
+	haystack: &core::ops::RangeInclusive<U>,
+	needle: &core::ops::RangeInclusive<U>,
+) -> bool {
+	haystack.contains(needle.start()) && haystack.contains(needle.end())
+}
+
+fn has_overlap<U: PartialOrd>(
+	a: &core::ops::RangeInclusive<U>,
+	b: &core::ops::RangeInclusive<U>,
+) -> bool {
+	a.contains(b.start())
+		|| a.contains(b.end())
+		|| b.contains(a.start())
+		|| b.contains(a.end())
+}
+
+pub fn part1() {
+	let sum = INPUT
+		.split('\n')
+		.filter(|s| !s.is_empty())
+		.map(|line| {
+			let mut elves = line.split(',');
+			let fst = elves.next().unwrap();
+			let fst = parse_range(fst);
+
+			let snd = elves.next().unwrap();
+			let snd = parse_range(snd);
+
+			u64::from(fully_contains(&fst, &snd) || fully_contains(&snd, &fst))
+		})
+		.sum::<uint>();
+
+	println!("{}", sum);
+}
+
+pub fn part2() {
+	let sum = INPUT
+		.split('\n')
+		.filter(|s| !s.is_empty())
+		.map(|line| {
+			let mut elves = line.split(',');
+			let fst = elves.next().unwrap();
+			let fst = parse_range(fst);
+
+			let snd = elves.next().unwrap();
+			let snd = parse_range(snd);
+
+			u64::from(has_overlap(&fst, &snd))
+		})
+		.sum::<uint>();
+
+	println!("{}", sum);
+}