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| 1 | +use crate::input_reader; |
| 2 | +use std::cmp::Ordering; |
| 3 | +use std::collections::VecDeque; |
| 4 | +use std::collections::HashMap; |
| 5 | +use std::hash::Hash; |
| 6 | +use std::hash::Hasher; |
| 7 | + |
| 8 | +type Cost = usize; |
| 9 | + |
| 10 | +#[derive(Debug, Clone, Copy)] |
| 11 | +struct Pos { |
| 12 | + x: i32, |
| 13 | + y: i32, |
| 14 | +} |
| 15 | + |
| 16 | +impl Hash for Pos { |
| 17 | + fn hash<H: Hasher>(&self, state: &mut H) { |
| 18 | + self.x.hash(state); |
| 19 | + self.y.hash(state); |
| 20 | + } |
| 21 | +} |
| 22 | + |
| 23 | +impl PartialEq for Pos { |
| 24 | + fn eq(&self, other: &Self) -> bool { |
| 25 | + self.x == other.x && self.y == other.y |
| 26 | + } |
| 27 | +} |
| 28 | +impl Eq for Pos {} |
| 29 | + |
| 30 | +#[derive(Debug, Eq)] |
| 31 | +struct Processable { |
| 32 | + pos: Pos, |
| 33 | + net_cost: Cost |
| 34 | +} |
| 35 | + |
| 36 | +impl Processable { |
| 37 | + pub fn new(pos: Pos, net_cost: Cost) -> Self { |
| 38 | + Processable { |
| 39 | + pos, |
| 40 | + net_cost |
| 41 | + } |
| 42 | + } |
| 43 | +} |
| 44 | + |
| 45 | +impl PartialOrd for Processable { |
| 46 | + fn partial_cmp(&self, other: &Self) -> Option<Ordering> { |
| 47 | + Some(self.cmp(other)) |
| 48 | + } |
| 49 | +} |
| 50 | + |
| 51 | +impl Ord for Processable { |
| 52 | + fn cmp(&self, other: &Self) -> Ordering { |
| 53 | + self.net_cost.cmp(&other.net_cost) |
| 54 | + } |
| 55 | +} |
| 56 | + |
| 57 | +impl PartialEq for Processable { |
| 58 | + fn eq(&self, other: &Self) -> bool { |
| 59 | + self.net_cost == other.net_cost |
| 60 | + } |
| 61 | +} |
| 62 | + |
| 63 | +fn get_neighbors(map: &Vec<Vec<i32>>, pos: Pos) -> Vec<Pos> { |
| 64 | + let w = map[0].len() as i32; |
| 65 | + let h = map.len() as i32; |
| 66 | + let points: Vec<(i32, i32)> = vec![(1, 0), (-1, 0), (0, 1), (0, -1)]; |
| 67 | + return points.iter().map(|&point| { |
| 68 | + let new_pos = Pos { x: pos.x + point.0, y: pos.y + point.1 }; |
| 69 | + if new_pos.x < 0 || |
| 70 | + new_pos.x >= w || |
| 71 | + new_pos.y < 0 || |
| 72 | + new_pos.y >= h |
| 73 | + { |
| 74 | + return None; |
| 75 | + } |
| 76 | + let a = map[pos.y as usize][pos.x as usize]; |
| 77 | + let b = map[new_pos.y as usize][new_pos.x as usize]; |
| 78 | + if a + 1 < b { |
| 79 | + return None; |
| 80 | + } |
| 81 | + return Some(new_pos); |
| 82 | + }).filter_map(|e| e).collect() |
| 83 | +} |
| 84 | + |
| 85 | +fn part1(map: &Vec<Vec<i32>>, start: Pos, end: Pos) { |
| 86 | + // A simplified version of Dijkstra. |
| 87 | + let mut processed: HashMap<Pos, Cost> = HashMap::new(); |
| 88 | + let mut to_process: VecDeque<Processable> = VecDeque::new(); |
| 89 | + to_process.push_back(Processable::new(start, 0)); |
| 90 | + processed.insert(start, 0); |
| 91 | + |
| 92 | + while to_process.len() > 0 { |
| 93 | + // Ensure elements are from least costly to most costly. |
| 94 | + to_process.make_contiguous().sort(); |
| 95 | + let processable = to_process.pop_front().unwrap(); |
| 96 | + for neighbor in get_neighbors(map, processable.pos) { |
| 97 | + let new_cost = processable.net_cost + 1; |
| 98 | + // Skip points that have already been processed |
| 99 | + if processed.contains_key(&neighbor) && processed[&neighbor] <= new_cost { |
| 100 | + continue; |
| 101 | + } |
| 102 | + processed.insert(neighbor, new_cost); |
| 103 | + to_process.push_back(Processable::new(neighbor, new_cost)); |
| 104 | + } |
| 105 | + } |
| 106 | + println!("Part 1: {}", processed.get(&end).unwrap()); |
| 107 | +} |
| 108 | + |
| 109 | +pub fn run() { |
| 110 | + let input = input_reader::read_file_in_cwd("src/day_12.data"); |
| 111 | + |
| 112 | + let lines: Vec<&str> = input.split("\n").collect(); |
| 113 | + let mut start_y = 0; |
| 114 | + let mut start_x = 0; |
| 115 | + let mut end_y = 0; |
| 116 | + let mut end_x = 0; |
| 117 | + let mut y = 0; |
| 118 | + let mut x = 0; |
| 119 | + let map: Vec<Vec<i32>> = lines.iter().map(|&val| { |
| 120 | + y += 1; |
| 121 | + x = 0; |
| 122 | + let cells: Vec<char> = val.chars().collect(); |
| 123 | + return cells.iter().map(|&val| { |
| 124 | + x += 1; |
| 125 | + // Make comparing values easier by converting special cases like S and E |
| 126 | + // as numeric values. |
| 127 | + if val == 'S' { |
| 128 | + start_x = x - 1; |
| 129 | + start_y = y - 1; |
| 130 | + return 'a' as i32 - 1 |
| 131 | + } else if val == 'E' { |
| 132 | + end_x = x - 1; |
| 133 | + end_y = y - 1; |
| 134 | + return 'z' as i32 + 1 |
| 135 | + } |
| 136 | + return val as i32 |
| 137 | + }).collect(); |
| 138 | + }).collect(); |
| 139 | + |
| 140 | + let start = Pos { x: start_x, y: start_y }; |
| 141 | + let end = Pos { x: end_x, y: end_y }; |
| 142 | + |
| 143 | + part1(&map, start, end); |
| 144 | +} |
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