Day 1, 2 and 3

day1/src/main.rs

@@ -0,0 +1,91 @@
+#![feature(test)]
+
+use std::{collections::BinaryHeap, fs::read_to_string};
+
+fn main() {
+    let input = read_to_string("input.txt").expect("need input file");
+    let (max, top3) = initial(&input);
+    println!("{max}, {top3}");
+    let (max, top3) = idiomatic(&input);
+    println!("{max}, {top3}");
+}
+
+fn idiomatic(input: &str) -> (u32, u32) {
+    let mut sums: BinaryHeap<_> = input
+        .split_terminator("\n\n")
+        .map(|block| {
+            block
+                .split_terminator('\n')
+                .map(|line| line.parse::<u32>().unwrap_or_default())
+                .sum()
+        })
+        .collect();
+    let max = sums.pop().unwrap_or_default();
+    let top3 = max + sums.pop().unwrap_or_default() + sums.pop().unwrap_or_default();
+    (max, top3)
+}
+
+fn initial(input: &str) -> (u32, u32) {
+    let numbers = input.split_terminator('\n').map(|s| s.parse::<u32>().ok());
+    let mut elves = vec![0];
+    for number in numbers {
+        match number {
+            Some(ration) => {
+                *elves.last_mut().unwrap() += ration;
+            }
+            None => elves.push(0),
+        }
+    }
+    let (index, max) = elves.iter().enumerate().max_by_key(|(_, v)| **v).unwrap();
+    let mut elves = elves.clone();
+    elves.remove(index);
+    let (index, second) = elves.iter().enumerate().max_by_key(|(_, v)| **v).unwrap();
+    let mut elves = elves.clone();
+    elves.remove(index);
+    let third = elves.iter().max().unwrap();
+    let top3 = max + second + third;
+    (*max, top3)
+}
+
+#[cfg(test)]
+mod tests {
+    use std::{
+        fs::File,
+        io::{BufRead, BufReader},
+    };
+
+    use super::*;
+    extern crate test;
+    use test::Bencher;
+
+    #[bench]
+    fn bench_initial(b: &mut Bencher) {
+        let input = read_to_string("input.txt").expect("need input file");
+        b.iter(|| initial(&input));
+    }
+
+    #[bench]
+    fn bench_idiomatic(b: &mut Bencher) {
+        let input = read_to_string("input.txt").expect("need input file");
+        b.iter(|| idiomatic(&input));
+    }
+
+    #[bench]
+    fn bench_read_string(b: &mut Bencher) {
+        b.iter(|| {
+            read_to_string("input.txt")
+                .unwrap()
+                .split_terminator('\n')
+                .for_each(drop);
+        });
+    }
+
+    #[bench]
+    fn bench_lines(b: &mut Bencher) {
+        b.iter(|| {
+            BufReader::new(File::open("input.txt").unwrap())
+                .lines()
+                .for_each(drop);
+        });
+    }
+}