day 1: problem 1 solution

1/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"

1/Cargo.toml

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+[package]
+name = "day1"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

1/src/main.rs

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+use std::fs::File;
+use std::io::{BufRead, BufReader, Lines};
+use std::iter::zip;
+use std::time::Instant;
+
+// BOILERPLATE
+type InputIter = Lines<BufReader<File>>;
+
+fn get_input() -> InputIter {
+    let f = File::open("input").unwrap();
+    let br = BufReader::new(f);
+    br.lines()
+}
+
+fn main() {
+    let start = Instant::now();
+    let ans1 = problem1(get_input());
+    let duration = start.elapsed();
+    println!("Problem 1 solution: {} [{}s]", ans1, duration.as_secs_f64());
+
+    let start = Instant::now();
+    let ans2 = problem2(get_input());
+    let duration = start.elapsed();
+    println!("Problem 2 solution: {} [{}s]", ans2, duration.as_secs_f64());
+}
+
+// PROBLEM 1 solution
+
+#[derive(Debug)]
+struct Entry {
+    pos: usize,
+    val: u32,
+}
+
+fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
+    let mut left = Vec::new();
+    let mut right = Vec::new();
+    for (pos, line) in input.enumerate() {
+        if line.is_err() {
+            panic!("can't read line");
+        }
+        let line = line.unwrap();
+        let parts: Vec<&str> = line.split_ascii_whitespace().collect();
+        left.push(Entry{pos, val: parts[0].parse::<u32>().unwrap()});
+        right.push(Entry{pos, val: parts[1].parse::<u32>().unwrap()});
+    }
+    left.sort_by_key(|entry| entry.val);
+    right.sort_by_key(|entry| entry.val);
+
+    println!("{:?}", right);
+    
+    zip(left, right).map(|(left, right)| { 
+        println!("{:?} {:?}", left, right);
+        u64::abs_diff(left.val as u64, right.val as u64)}).sum()
+}
+
+// PROBLEM 2 solution
+fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
+    0
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::*;
+    use std::io::Cursor;
+
+    const EXAMPLE: &str = &"3   4
+4   3
+2   5
+1   3
+3   9
+3   3";
+
+    #[test]
+    fn problem1_example() {
+        let c = Cursor::new(EXAMPLE);
+        assert_eq!(problem1(c.lines()), 11);
+    }
+
+    #[test]
+    fn problem2_example() {
+        let c = Cursor::new(EXAMPLE);
+        assert_eq!(problem2(c.lines()), 0);
+    }
+}