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| 1 | +use std::collections::HashMap; |
| 2 | + |
| 3 | +fn main() { |
| 4 | + let input = include_str!("../day01.txt"); |
| 5 | + |
| 6 | + println!("Part 1: {}", part1(input)); |
| 7 | + println!("Part 2: {}", part2(input)); |
| 8 | +} |
| 9 | + |
| 10 | +fn part1(input: &str) -> i32 { |
| 11 | + let (mut lefts, mut rights): (Vec<_>, Vec<_>) = input |
| 12 | + .lines() |
| 13 | + .map(|line| { |
| 14 | + let mut nums = line |
| 15 | + .split_whitespace() |
| 16 | + .map(|num| num.parse::<i32>().unwrap()); |
| 17 | + let a = nums.next().unwrap(); |
| 18 | + let b = nums.next().unwrap(); |
| 19 | + |
| 20 | + (a, b) |
| 21 | + }) |
| 22 | + .unzip(); |
| 23 | + |
| 24 | + lefts.sort(); |
| 25 | + rights.sort(); |
| 26 | + |
| 27 | + lefts |
| 28 | + .into_iter() |
| 29 | + .zip(rights) |
| 30 | + .fold(0, |acc, (a, b)| acc + (b - a).abs()) |
| 31 | +} |
| 32 | + |
| 33 | +fn part2(input: &str) -> i32 { |
| 34 | + let (lefts, rights): (Vec<_>, Vec<_>) = input |
| 35 | + .lines() |
| 36 | + .map(|line| { |
| 37 | + let mut nums = line |
| 38 | + .split_whitespace() |
| 39 | + .map(|num| num.parse::<i32>().unwrap()); |
| 40 | + let a = nums.next().unwrap(); |
| 41 | + let b = nums.next().unwrap(); |
| 42 | + |
| 43 | + (a, b) |
| 44 | + }) |
| 45 | + .unzip(); |
| 46 | + |
| 47 | + let mut counts: HashMap<i32, i32> = HashMap::new(); |
| 48 | + |
| 49 | + for n in &lefts { |
| 50 | + if !counts.contains_key(n) { |
| 51 | + counts.insert(*n, 0); |
| 52 | + } |
| 53 | + } |
| 54 | + |
| 55 | + for n in rights { |
| 56 | + if let Some(count) = counts.get_mut(&n) { |
| 57 | + *count += 1; |
| 58 | + } |
| 59 | + } |
| 60 | + |
| 61 | + lefts.into_iter().map(|n| n * counts[&n]).sum() |
| 62 | +} |
| 63 | + |
| 64 | +#[cfg(test)] |
| 65 | +mod tests { |
| 66 | + use super::*; |
| 67 | + |
| 68 | + const TEST_INPUT: &str = "3 4 |
| 69 | +4 3 |
| 70 | +2 5 |
| 71 | +1 3 |
| 72 | +3 9 |
| 73 | +3 3"; |
| 74 | + |
| 75 | + #[test] |
| 76 | + fn test_part1() { |
| 77 | + assert_eq!(part1(TEST_INPUT), 11); |
| 78 | + } |
| 79 | + |
| 80 | + #[test] |
| 81 | + fn test_part2() { |
| 82 | + assert_eq!(part2(TEST_INPUT), 31); |
| 83 | + } |
| 84 | +} |
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