Day 1, puzzle 2

src/bin/d1p2.rs

@@ -0,0 +1,15 @@
+use aoc22::day1;
+use aoc22::util;
+
+const N_ELVES: usize = 3;
+
+fn main() {
+    let elves = day1::read_elves();
+
+    let max_vals = util::max_n(elves.as_slice(), N_ELVES).unwrap();
+    println!(
+        "The {} elves with the most calories are carrying {} cal",
+        N_ELVES,
+        max_vals.iter().sum::<u32>()
+    );
+}

src/lib.rs

@@ -1 +1,2 @@
 pub mod day1;
+pub mod util;

src/util.rs

@@ -0,0 +1,24 @@
+pub fn max_n<T: Ord + Copy>(slice: &[T], n: usize) -> Result<Vec<T>, ()> {
+    if n == 0 || n > slice.len() {
+        return Err(());
+    }
+    let mut max_vals = Vec::new();
+    for _ in 0..n {
+        max_vals.push(slice[0]);
+    }
+
+    for val in slice {
+        if val > &max_vals[0] {
+            max_vals[2] = max_vals[1];
+            max_vals[1] = max_vals[0];
+            max_vals[0] = *val;
+        } else if val > &max_vals[1] {
+            max_vals[2] = max_vals[1];
+            max_vals[1] = *val;
+        } else if val > &max_vals[2] {
+            max_vals[2] = *val;
+        }
+    }
+
+    Ok(max_vals)
+}