Day 12 part 2
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5B2020A0F9921EF4
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@ -3,11 +3,100 @@ use std::collections::HashSet;
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mod common;
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type Input = (Vec<Vec<u8>>, (usize, usize), (usize, usize));
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struct Input {
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map: Vec<Vec<u8>>,
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start: (usize, usize),
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end: (usize, usize),
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}
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type Answer = usize;
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impl Input {
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fn shortest_path_length(&self, s: Option<(usize, usize)>) -> usize {
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let s = s.unwrap_or(self.start);
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let mut open_set = HashSet::<(usize, usize)>::from([s]);
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let mut came_from = HashMap::<(usize, usize), (usize, usize)>::new();
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let mut cheapest_for = HashMap::<(usize, usize), i64>::from([(s, 0)]);
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let mut guess_score = HashMap::<(usize, usize), i64>::from([(s, 0)]);
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let h = self.map.len();
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let w = self.map[0].len();
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// guess_score.get(&(y, x)).unwrap_or(&i64::MAX).clone()
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while open_set.len() > 0 {
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let (mut y, mut x) = open_set
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.iter()
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.min_by(|(y1, x1), (y2, x2)| {
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guess_score
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.get(&(*y1, *x1))
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.unwrap_or(&i64::MAX)
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.cmp(&guess_score.get(&(*y2, *x2)).unwrap_or(&i64::MAX))
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})
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.unwrap();
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if (y, x) == self.end {
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let mut n = 0;
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while let Some((ny, nx)) = came_from.get(&(y, x)) {
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y = *ny;
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x = *nx;
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n += 1;
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}
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return n;
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}
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open_set.remove(&(y, x));
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let c = self.map[y][x];
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let mut potential_neighbors = vec![];
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if y > 0 {
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potential_neighbors.push((y - 1, x));
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}
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if y < h - 1 {
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potential_neighbors.push((y + 1, x));
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}
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if x > 0 {
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potential_neighbors.push((y, x - 1));
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}
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if x < w - 1 {
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potential_neighbors.push((y, x + 1));
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}
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for (ny, nx) in potential_neighbors
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.iter()
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.filter(|(y, x)| (self.map[*y][*x] as i32) - (c as i32) <= 1)
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{
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let ny = ny.clone();
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let nx = nx.clone();
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let score = guess_score.get(&(y, x)).unwrap_or(&i64::MAX).clone() + 1;
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let ns = guess_score.get(&(ny, nx)).unwrap_or(&i64::MAX).clone();
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if score < ns {
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came_from.insert((ny, nx), (y, x));
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guess_score.insert((ny, nx), score);
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cheapest_for.insert((ny, nx), score + 1);
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open_set.insert((ny, nx));
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}
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}
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}
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let mut distances: Vec<Vec<usize>> = vec![];
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let mut previous_bests: Vec<Vec<Option<(usize, usize)>>> = vec![];
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for y in 0..self.map.len() {
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let mut row_distances = vec![];
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let mut row_previous_bests = vec![];
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for _ in 0..self.map[y].len() {
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row_distances.push(std::usize::MAX);
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row_previous_bests.push(None);
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}
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distances.push(row_distances);
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previous_bests.push(row_previous_bests);
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}
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distances[s.0][s.1] = 0;
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// no path found
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usize::MAX
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}
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}
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fn processed_input(input: &str) -> Input {
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let mut result = vec![];
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let mut map = vec![];
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let mut start = (0, 0);
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let mut end = (0, 0);
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let lines = input
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@ -30,110 +119,37 @@ fn processed_input(input: &str) -> Input {
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c => row.push(c as u8 - 'a' as u8),
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}
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}
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result.push(row)
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map.push(row)
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}
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return (result, start, end);
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return Input { map, start, end };
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}
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fn part1(input: &Input) -> Answer {
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let mut open_set = HashSet::<(usize, usize)>::from([input.1]);
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let mut came_from = HashMap::<(usize, usize), (usize, usize)>::new();
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let mut cheapest_for = HashMap::<(usize, usize), i64>::from([(input.1, 0)]);
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let mut guess_score = HashMap::<(usize, usize), i64>::from([(input.1, 0)]);
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let h = input.0.len();
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let w = input.0[0].len();
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// guess_score.get(&(y, x)).unwrap_or(&i64::MAX).clone()
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while open_set.len() > 0 {
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let (mut y, mut x) = open_set
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.iter()
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.min_by(|(y1, x1), (y2, x2)| {
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guess_score
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.get(&(*y1, *x1))
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.unwrap_or(&i64::MAX)
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.cmp(&guess_score.get(&(*y2, *x2)).unwrap_or(&i64::MAX))
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})
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.unwrap();
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if (y, x) == input.2 {
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let mut n = 0;
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while let Some((ny, nx)) = came_from.get(&(y, x)) {
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y = *ny;
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x = *nx;
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n += 1;
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}
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return n;
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}
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open_set.remove(&(y, x));
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let c = input.0[y][x];
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let mut potential_neighbors = vec![];
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if y > 0 {
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potential_neighbors.push((y - 1, x));
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}
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if y < h - 1 {
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potential_neighbors.push((y + 1, x));
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}
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if x > 0 {
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potential_neighbors.push((y, x - 1));
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}
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if x < w - 1 {
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potential_neighbors.push((y, x + 1));
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}
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for (ny, nx) in potential_neighbors
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.iter()
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.filter(|(y, x)| (input.0[*y][*x] as i32) - (c as i32) <= 1)
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{
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let ny = ny.clone();
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let nx = nx.clone();
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let score = guess_score.get(&(y, x)).unwrap_or(&i64::MAX).clone() + 1;
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let ns = guess_score.get(&(ny, nx)).unwrap_or(&i64::MAX).clone();
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if score < ns {
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came_from.insert((ny, nx), (y, x));
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guess_score.insert((ny, nx), score);
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cheapest_for.insert((ny, nx), score + 1);
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open_set.insert((ny, nx));
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}
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}
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}
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let mut distances: Vec<Vec<usize>> = vec![];
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let mut previous_bests: Vec<Vec<Option<(usize, usize)>>> = vec![];
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for y in 0..input.0.len() {
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let mut row_distances = vec![];
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let mut row_previous_bests = vec![];
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for _ in 0..input.0[y].len() {
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row_distances.push(std::usize::MAX);
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row_previous_bests.push(None);
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}
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distances.push(row_distances);
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previous_bests.push(row_previous_bests);
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}
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distances[input.1 .0][input.1 .1] = 0;
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// no path found
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usize::MAX
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input.shortest_path_length(None)
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}
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fn part2(input: &Input) -> Answer {
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let mut possible_starts = HashSet::<(usize, usize)>::from([input.1]);
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for y in 0..input.0.len() {
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for x in 0..input.0[y].len() {
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if input.0[y][x] == 0 {
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fn part2(input: Input) -> Answer {
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let mut possible_starts = HashSet::<(usize, usize)>::from([input.start]);
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for y in 0..input.map.len() {
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for x in 0..input.map[y].len() {
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if input.map[y][x] == 0 {
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possible_starts.insert((y, x));
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}
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}
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}
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possible_starts.iter().map(|s| part1((input.0, s, input.2))
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}
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possible_starts
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.iter()
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.map(|s| input.shortest_path_length(Some(*s)))
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.min()
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.unwrap()
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}
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fn main() {
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let input_text = common::day_input(12);
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eprintln!("{}\n\nAbove is your input file.\n\n", input_text);
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let input = processed_input(&input_text);
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common::show_answers(&part1(&input), &part2(&input))
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common::show_answers(&part1(&input), &part2(input))
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// common::show_both_answers(&both_parts(&input))
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}
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@ -155,7 +171,7 @@ abdefghi";
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fn test() {
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let input = processed_input(TEST_INPUT);
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assert_eq!(part1(&input), 31);
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assert_eq!(part2(&input), 0);
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assert_eq!(part2(input), 29);
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// assert_eq!(both_parts(&input), (0, 0));
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}
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}
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