97 lines
3.0 KiB
Rust
97 lines
3.0 KiB
Rust
use core::panic;
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use std::collections::{HashMap, HashSet};
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use utils::{math::factorial, permutation::nth_lex};
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pub fn process_part1(input: &str) -> u32 {
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let mut distances = HashMap::new();
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let mut locations = HashSet::new();
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input.lines().for_each(|line| {
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let (direction, distance) = line.split_once(" = ").unwrap();
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let (from, to) = direction.split_once(" to ").unwrap();
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let distance = distance.parse::<u32>().unwrap();
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distances.insert((from.to_string(), to.to_string()), distance);
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locations.insert(from.to_string());
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locations.insert(to.to_string());
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});
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let locations = locations
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.iter()
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.map(|place| place.to_string())
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.collect::<Vec<String>>();
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let num_permutations = factorial(locations.len().try_into().unwrap());
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let mut shortest = u32::MAX;
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for idx in 1..=num_permutations {
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let perm = nth_lex(locations.clone(), idx.try_into().unwrap()).unwrap();
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let route_length = get_route_length(perm, &distances);
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if route_length < shortest {
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shortest = route_length;
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}
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}
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shortest
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}
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fn get_route_length(route: Vec<String>, distances: &HashMap<(String, String), u32>) -> u32 {
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route
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.windows(2)
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.map(|pair| {
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let distance = distances.get(&(pair[0].clone(), pair[1].clone()));
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if let Some(distance) = distance {
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return distance;
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}
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let distance = distances.get(&(pair[1].clone(), pair[0].clone()));
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if let Some(distance) = distance {
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return distance;
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}
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panic!("Should not happen");
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})
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.sum()
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}
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pub fn process_part2(input: &str) -> u32 {
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let mut distances = HashMap::new();
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let mut locations = HashSet::new();
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input.lines().for_each(|line| {
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let (direction, distance) = line.split_once(" = ").unwrap();
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let (from, to) = direction.split_once(" to ").unwrap();
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let distance = distance.parse::<u32>().unwrap();
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distances.insert((from.to_string(), to.to_string()), distance);
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locations.insert(from.to_string());
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locations.insert(to.to_string());
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});
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let locations = locations
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.iter()
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.map(|place| place.to_string())
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.collect::<Vec<String>>();
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let num_permutations = factorial(locations.len().try_into().unwrap());
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let mut longest = 0;
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for idx in 1..=num_permutations {
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let perm = nth_lex(locations.clone(), idx.try_into().unwrap()).unwrap();
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let route_length = get_route_length(perm, &distances);
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if route_length > longest {
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longest = route_length;
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}
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}
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longest
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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const INPUT: &str = "London to Dublin = 464
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London to Belfast = 518
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Dublin to Belfast = 141";
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#[test]
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fn part1() {
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let result = process_part1(INPUT);
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assert_eq!(result, 605);
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}
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#[test]
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fn part2() {
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let result = process_part2(INPUT);
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assert_eq!(result, 982);
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}
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}
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