Day 1 solution

flake.lock

@@ -17,11 +17,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1669418739,
+        "lastModified": 1669764884,
-        "narHash": "sha256-T86oFvcUIRwHWBWUt7WjaP4BP/3lDGbv5AppQSI1FkI=",
+        "narHash": "sha256-1qWR/5+WtqxSedrFbUbM3zPMO7Ec2CGWaxtK4z4DdvY=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "695b3515251873e0a7e2021add4bba643c56cde3",
+        "rev": "0244e143dc943bcf661fdaf581f01eb0f5000fcf",
         "type": "github"
       },
       "original": {
@@ -52,7 +52,7 @@
         "nixpkgs": "nixpkgs_2"
       },
       "locked": {
-        "narHash": "sha256-xMOq9ifVo63/aBA1VIHQQ4riuRJGyup7F1orjekAwpk=",
+        "narHash": "sha256-/ar+cbAKAxd2Ng9b7EhrIMz9CP353RbmLecvyOidyUM=",
         "type": "tarball",
         "url": "https://github.com/oxalica/rust-overlay/archive/master.tar.gz"
       },

problems/src/day1.rs

@@ -1,25 +1,100 @@
 const PART1: &str = include_str!("../data/day1a.txt");
 
 pub fn part1() -> String {
-    let lines = PART1.lines();
+    format!("{}", max_calories(sum_calories(input_data(PART1))).1)
-
-    let depths: Vec<i32> = lines.map(|l| l.parse::<i32>().unwrap()).collect();
-
-    let depths_a = depths.iter();
-    let depths_b = depths.iter().skip(1);
-    let depth_cmp = depths_a.zip(depths_b);
-
-    let increases = depth_cmp.fold(0, |cur, (a, b)| {
-        println!("{} < {}? {}", a, b, a < b);
-        if a < b {
-            cur + 1
-        } else {
-            cur
-        }
-    });
-    format!("{}", increases)
 }
 
 pub fn part2() -> String {
-    "no response".to_owned()
+    format!("{}", max_three_calories(sum_calories(input_data(PART1))))
+}
+
+fn input_data(data: &str) -> Vec<Vec<u32>> {
+    data.lines()
+        .collect::<Vec<&str>>()
+        .split(|l| *l == "")
+        .map(|v| {
+            v.into_iter()
+                .map(|element| element.parse::<u32>().unwrap())
+                .collect::<Vec<u32>>()
+        })
+        .collect::<Vec<Vec<u32>>>()
+}
+
+fn sum_calories(food_lists: Vec<Vec<u32>>) -> Vec<(usize, u32)> {
+    food_lists
+        .into_iter()
+        .map(|list| list.into_iter().fold(0, |cur, val| cur + val))
+        .enumerate()
+        .collect::<Vec<(usize, u32)>>()
+}
+
+fn elf_with_most_calories(batch_calories: Vec<(usize, u32)>) -> usize {
+    let (idx, _) = max_calories(batch_calories);
+    // Elves are 1-indexed
+    return idx + 1;
+}
+
+fn max_calories(mut batch_calories: Vec<(usize, u32)>) -> (usize, u32) {
+    batch_calories.sort_by(|(_, val1), (_, val2)| val1.cmp(val2));
+    batch_calories.reverse();
+    batch_calories[0]
+}
+
+fn max_three_calories(mut batch_calories: Vec<(usize, u32)>) -> u32 {
+    batch_calories.sort_by(|(_, val1), (_, val2)| val1.cmp(val2));
+    batch_calories.reverse();
+    batch_calories
+        .into_iter()
+        .take(3)
+        .fold(0, |cur, (_, val)| cur + val)
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const TEST_DATA1: &str = "1000
+2000
+3000
+
+4000
+
+5000
+6000
+
+7000
+8000
+9000
+
+10000";
+    #[test]
+    fn find_most_elf() {
+        let input = input_data(TEST_DATA1);
+        let food_batches = sum_calories(input);
+        assert_eq!(
+            food_batches,
+            vec![6000, 4000, 11000, 24000, 10000]
+                .into_iter()
+                .enumerate()
+                .collect::<Vec<(usize, u32)>>()
+        );
+
+        assert_eq!(elf_with_most_calories(food_batches.clone()), 4);
+        assert_eq!(max_calories(food_batches), (3, 24000));
+    }
+
+    #[test]
+    fn batch_with_one_element() {
+        let input = input_data("50057");
+        let food_batches = sum_calories(input);
+        assert_eq!(food_batches, vec![(0, 50057)]);
+    }
+
+    #[test]
+    fn find_max_three() {
+        assert_eq!(
+            max_three_calories(sum_calories(input_data(TEST_DATA1))),
+            45000
+        );
+    }
 }

problems/src/main.rs

@@ -2,13 +2,12 @@ mod day1;
 
 fn main() {
     let day = std::env::args().skip(1).next();
-    println!("day: {:?}", day);
 
     let result = match day.as_ref().map(|v| v.as_ref()) {
-        Some("day1a") => day1::part1(),
+        Some("1a") => day1::part1(),
-        Some("day1b") => day1::part2(),
+        Some("1b") => day1::part2(),
         _ => panic!("unrecognized day"),
     };
 
-    println!("{:?} Result: {}", day, result);
+    println!("[{}] {}", day.unwrap(), result);
 }