complete day 4

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+/// --- Day 4: Camp Cleanup ---
+///
+/// Space needs to be cleared before the last supplies can be unloaded from the ships, and so
+/// several Elves have been assigned the job of cleaning up sections of the camp.  Every section
+/// has a unique ID number, and each Elf is assigned a range of section IDs.
+///
+/// However, as some of the Elves compare their section assignments with each other, they've
+/// noticed that many of the assignments overlap.  To try to quickly find overlaps and reduce
+/// duplicated effort, the Elves pair up and make a big list of the section assignments for each
+/// pair (your puzzle input).
+///
+/// For example, consider the following list of section assignment 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
+/// ```
+///
+/// For the first few pairs, this list means:
+///
+///     Within the first pair of Elves, the first Elf was assigned sections 2-4 (sections 2, 3, and
+///     4), while the second Elf was assigned sections 6-8 (sections 6, 7, 8).
+///     The Elves in the second pair were each assigned two sections.
+///     The Elves in the third pair were each assigned three sections: one got sections 5, 6, and
+///     7, while the other also got 7, plus 8 and 9.
+///
+/// This example list uses single-digit section IDs to make it easier to draw; your actual list
+/// might contain larger numbers. Visually, these pairs of section assignments look like this:
+///
+/// .234.....  2-4
+/// .....678.  6-8
+///
+/// .23......  2-3
+/// ...45....  4-5
+///
+/// ....567..  5-7
+/// ......789  7-9
+///
+/// .2345678.  2-8
+/// ..34567..  3-7
+///
+/// .....6...  6-6
+/// ...456...  4-6
+///
+/// .23456...  2-6
+/// ...45678.  4-8
+///
+/// Some of the pairs have noticed that one of their assignments fully contains the other.  For
+/// example, 2-8 fully contains 3-7, and 6-6 is fully contained by 4-6.  In pairs where one
+/// assignment fully contains the other, one Elf in the pair would be exclusively cleaning sections
+/// their partner will already be cleaning, so these seem like the most in need of
+/// reconsideration.  In this example, there are 2 such pairs.
+///
+/// In how many assignment pairs does one range fully contain the other?
+use clap::Parser;
+use itertools::Itertools;
+
+use std::fs::File;
+use std::io::prelude::*;
+use std::io::BufReader;
+use std::path::PathBuf;
+
+const FILEPATH: &'static str = "examples/input.txt";
+
+#[derive(Parser, Debug)]
+#[clap(author, version, about, long_about = None)]
+struct Cli {
+    #[clap(short, long, default_value = FILEPATH)]
+    file: PathBuf,
+}
+
+fn main() {
+    let args = Cli::parse();
+
+    let file = File::open(&args.file).unwrap();
+    let reader = BufReader::new(file);
+    let res = reader
+        .lines()
+        .map(|l| {
+            l.unwrap()
+                .split(',')
+                .map(|s| {
+                    s.split('-')
+                        .map(|v| v.parse::<usize>().unwrap())
+                        .collect_tuple::<(usize, usize)>()
+                        .unwrap()
+                })
+                .collect_tuple::<((usize, usize), (usize, usize))>()
+                .unwrap()
+        })
+        .filter(|((l1, l2), (r1, r2))| (l1 <= r1 && l2 >= r2) || (r1 <= l1 && r2 >= l2))
+        .count();
+
+    println!("{res}");
+}