From c93e15720de529fba6d73f1f9bbf45f391698c5f Mon Sep 17 00:00:00 2001
From: Greg Burri <greg.burri@gmail.com>
Date: Sun, 4 Dec 2022 19:02:40 +0100
Subject: [PATCH] Day 4

---
 src/day04.rs | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.rs  |  7 +++++++
 2 files changed, 61 insertions(+)
 create mode 100644 src/day04.rs

diff --git a/src/day04.rs b/src/day04.rs
new file mode 100644
index 0000000..42302fd
--- /dev/null
+++ b/src/day04.rs
@@ -0,0 +1,54 @@
+use regex::Regex;
+
+type Pair = ((i32, i32), (i32, i32));
+
+pub fn parse(s: &str) -> Vec<Pair> {
+    let mut sections = Vec::new();
+    let r = Regex::new(r"^(\d+)-(\d+),(\d+)-(\d+)$").unwrap();
+    for l in s.lines() {
+        let cap = r.captures(l).unwrap();
+        sections.push(((cap[1].parse::<i32>().unwrap(), cap[2].parse::<i32>().unwrap()), (cap[3].parse::<i32>().unwrap(), cap[4].parse::<i32>().unwrap())));
+    }
+    return sections;
+}
+
+pub fn number_fully_contain(pairs: &[Pair]) -> i32 {
+    pairs.iter().filter_map(|((a1, a2), (b1, b2))| {
+        if a1 <= b1 && a2 >= b2 || b1 <= a1 && b2 >= a2 { Some(1) } else { None }
+    }).sum()
+}
+
+pub fn number_overlaps(pairs: &[Pair]) -> i32 {
+    pairs.iter().filter_map(|((a1, a2), (b1, b2))| {
+        if a2 >= b1 && a1 <= b2 { Some(1) } else { None }
+    }).sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1() {
+        let pairs ="2-4,6-8
+2-3,4-5
+5-7,7-9
+2-8,3-7
+6-6,4-6
+2-6,4-8";
+
+        assert_eq!(number_fully_contain(&parse(pairs)), 2);
+    }
+
+    #[test]
+    fn part2() {
+        let pairs ="2-4,6-8
+2-3,4-5
+5-7,7-9
+2-8,3-7
+6-6,4-6
+2-6,4-8";
+
+        assert_eq!(number_overlaps(&parse(pairs)), 4);
+    }
+}
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index e7b4bed..014c31d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,6 +4,7 @@ mod common;
 mod day01;
 mod day02;
 mod day03;
+mod day04;
 
 fn day01() -> String {
     let f = fs::File::open("data/day01.input").unwrap();
@@ -24,6 +25,11 @@ fn day03() -> String {
     format!("part1: {}, part2: {}", day03::priority_sum(&rucksacks), day03::badge_sum(&rucksacks))
 }
 
+fn day04() -> String {
+    let pairs = day04::parse(&fs::read_to_string("data/day04.input").unwrap());
+    format!("part1: {}, part2: {}", day04::number_fully_contain(&pairs), day04::number_overlaps(&pairs))
+}
+
 fn format_micros(t: u128) -> String {
     if t < 10_000 {
         format!("{} μs", t)
@@ -46,6 +52,7 @@ fn main() {
         day01,
         day02,
         day03,
+        day04,
     );
 
     let args: Vec<String> = env::args().skip(1).collect();
-- 
2.45.2