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day01.rs
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use std::collections::HashMap;
fn process_input(input: &str) -> Vec<(i32, i32)> {
input
.lines()
.map(|line| {
if line.is_empty() {
return (0, 0);
}
let mut nums = line.split_whitespace().map(|n| n.parse::<i32>().unwrap());
(nums.next().unwrap(), nums.next().unwrap())
})
.collect()
}
pub fn part_one(input: &str) -> i32 {
let (mut left, mut right): (Vec<i32>, Vec<i32>) = process_input(input).iter().cloned().unzip();
left.sort();
right.sort();
left.iter()
.zip(right.iter())
.map(|(l, r)| (r - l).abs())
.sum()
}
pub fn part_two(input: &str) -> i32 {
let (mut left, mut right): (Vec<i32>, Vec<i32>) = process_input(input).iter().cloned().unzip();
let mut map: HashMap<i32, i32> = HashMap::new();
left.sort();
right.sort();
left.iter()
.map(|l| {
if let Some(v) = map.get(l) {
return *v;
}
let count = right.iter().filter(|&r| r == l).count();
let product = *l * (count as i32);
map.insert(*l, product);
product
})
.sum()
}
#[cfg(test)]
mod tests {
use super::*;
const INPUT: &str = "3 4
4 3
2 5
1 3
3 9
3 3";
#[test]
fn test_part_one() {
let result = part_one(INPUT);
assert_eq!(result, 11);
}
#[test]
fn test_part_two() {
let result = part_two(INPUT);
assert_eq!(result, 31);
}
}