finish day 1, part 2

src/day_1.rs

@@ -1,8 +1,4 @@
-use std::fs;
-
-pub fn day_1() -> String {
-    let input = fs::read_to_string("input/day_1.txt").unwrap();
-
+pub fn part_1(input: &String) -> String {
     let elves: Vec<&str> = input.split("\n\n").collect();
 
     let mut highest_calorie_count: u64 = 0;
@@ -21,3 +17,18 @@ pub fn day_1() -> String {
 
     format!("{highest_calorie_count}")
 }
+
+pub fn part_2(input: &String) -> u64 {
+    let mut elf_calorie_counts: Vec<u64> = input.split("\n\n").map(|elf| {
+        elf.split_whitespace().map(|meal| meal.parse().unwrap_or(0)).sum()
+    }).collect();
+
+    elf_calorie_counts.sort_unstable();
+
+    let start = elf_calorie_counts.len() - 3;
+    let top_3 = elf_calorie_counts.drain(start..);
+
+    println!("Top 3 elves: {:?}", top_3);
+
+    top_3.sum()
+}

src/main.rs

@@ -1,5 +1,7 @@
 mod day_1;
 
 fn main() {
-    println!("{}", day_1::day_1());
+    let day_1_input = std::fs::read_to_string("input/day_1.txt").unwrap();
+    println!("Day 1, part 1: {}",   day_1::part_1(&day_1_input));
+    println!("Day 1, part 2: {:?}", day_1::part_2(&day_1_input));
 }