back adding day 1:

day1/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day1"
+version = "0.1.0"

day1/Cargo.toml

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+[package]
+name = "day1"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day1/src/main.rs

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+use std::fs::File;
+use std::io::{prelude::*, BufReader};
+
+fn main() -> std::io::Result<()>{
+    let file = File::open("input")?;
+    let reader = BufReader::new(file);
+
+    let mut elves = reader.lines()
+        .fold(Vec::new(), |mut acc, line| {
+            let line = line.unwrap();
+            //empty lines mean new elf
+            if line.is_empty() || acc.is_empty() {
+                acc.push(0_u64);
+            }
+
+            // the first time through is an edge case preventing an else here
+            if ! line.is_empty() {
+                let last = acc.last_mut().unwrap();
+                *last += line.parse::<u64>().unwrap();
+            }
+            acc
+        });
+
+    //order the elves since we don't care about position anymore
+    elves.sort();
+    let max = elves.len() - 1;
+
+    //part 1 is get the max
+    println!("Part 1: {}", elves[max]);
+
+    //Part 2 is get the sum of the largest 3
+    let counts: u64 = elves[(max-2)..].iter().sum();
+    println!("Part 2: {counts}");
+
+    Ok(())
+}