complete day 4

1 files changed, 57 insertions, 0 deletions

diff --git a/day04b/src/main.rs b/day04b/src/main.rs
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+/// --- Part Two ---
+///
+/// It seems like there is still quite a bit of duplicate work planned.  Instead, the Elves would
+/// like to know the number of pairs that overlap at all.
+///
+/// In the above example, the first two pairs (2-4,6-8 and 2-3,4-5) don't overlap, while the
+/// remaining four pairs (5-7,7-9, 2-8,3-7, 6-6,4-6, and 2-6,4-8) do overlap:
+///
+///     5-7,7-9 overlaps in a single section, 7.
+///     2-8,3-7 overlaps all of the sections 3 through 7.
+///     6-6,4-6 overlaps in a single section, 6.
+///     2-6,4-8 overlaps in sections 4, 5, and 6.
+///
+/// So, in this example, the number of overlapping assignment pairs is 4.
+///
+/// In how many assignment pairs do the ranges overlap?
+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 > r2 || r1 > l2))
+        .count();
+
+    println!("{res}");
+}