First star complete

Cargo.toml

@@ -2,7 +2,7 @@
 name = "aoc-vv"
 version = "0.1.0"
 edition = "2021"
-default-run = "p03"
+default-run = "p04"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 

src/bin/p04.rs

@@ -0,0 +1,63 @@
+#![feature(iterator_try_collect, iter_collect_into)]
+
+use std::fs;
+use std::io::{self, BufRead};
+use std::ops::Range;
+use std::str::FromStr;
+
+#[derive(Debug)]
+struct WorkRange(Range<u32>);
+
+impl WorkRange {
+    fn fully_contains(&self, other: &Self) -> bool {
+        self.0.start <= other.0.start && self.0.end >= other.0.end
+    }
+}
+
+impl FromStr for WorkRange {
+    type Err = <u32 as FromStr>::Err;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let spl: Vec<u32> = s.split('-').map(|n| n.parse()).try_collect()?;
+        Ok(WorkRange(spl[0]..spl[1]))
+    }
+}
+
+#[derive(Debug)]
+struct ElfPair(WorkRange, WorkRange);
+
+impl FromStr for ElfPair {
+    type Err = <WorkRange as FromStr>::Err;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let spl: Vec<&str> = s.split(',').collect();
+        Ok(ElfPair(spl[0].parse()?, spl[1].parse()?))
+    }
+}
+
+fn main() {
+    let filename = "etc/p04.txt";
+    let file = fs::File::open(filename).expect("Can't open file");
+    let reader = io::BufReader::new(file);
+
+    println!("PART ONE ---------------");
+    let pairs: Vec<ElfPair> = reader
+        .lines()
+        .flat_map(|l| l.expect("Expect valid line").parse())
+        .collect();
+
+    part1(&pairs);
+
+    println!("\n PART TWO ---------------");
+    part2(&pairs);
+}
+
+fn part1(pairs: &[ElfPair]) {
+    let sum = pairs
+        .iter()
+        .filter(|ElfPair(l, r)| l.fully_contains(r) || r.fully_contains(l))
+        .count();
+    println!("num containing: {}", sum);
+}
+
+fn part2(_pairs: &[ElfPair]) {}