Day 21 (late; I got filtered)
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@ -0,0 +1,271 @@
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use crate::util::maps::Direction;
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use std::collections::HashMap;
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const DPADS: usize = 25;
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pub fn day21() {
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let sequences: Vec<String> = crate::input(21).lines().map(|l| l.to_string()).collect();
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let mut memo: HashMap<(String, usize), u64> = HashMap::new();
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fn deeper(s: String, depth: usize, memo: &mut HashMap<(String, usize), u64>) -> u64 {
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// if this is already in deep lut, return
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if let Some(&expanded_size) = memo.get(&(s.to_string(), depth)) {
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return expanded_size;
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}
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// if this is two characters at the end, add expanded size to deep lut, and return
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if depth == 1 {
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let expanded_size = expand_dpad_string(&s).len() as u64;
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memo.insert((s, depth), expanded_size);
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return expanded_size;
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}
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// otherwise 1. expand, 2. split into substrings, and 3. recur for each substring
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let expanded = expand_dpad_string(&s);
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// 2. get substrings split by A (but including the A characters at the end of each substring)
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let substrings: Vec<String> = expanded
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.split_terminator("A")
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.map(|substring| {
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let mut substring = substring.to_string();
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substring.push_str("A");
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substring
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})
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.collect();
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let mut total: u64 = 0;
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for substring in substrings {
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let final_expanded_size = deeper(substring, depth - 1, memo);
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total += final_expanded_size;
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}
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memo.insert((s, depth), total);
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total
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}
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let mut complexity: u64 = 0;
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for sequence in sequences.iter() {
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let first_dpad_steps = expand_numpad_string(sequence);
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let length = deeper(first_dpad_steps.clone(), DPADS, &mut memo);
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let numeric = sequence
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.chars()
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.filter(|c| c.is_numeric())
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.collect::<String>()
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.parse::<u64>()
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.unwrap();
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complexity += length * numeric;
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}
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println!("Total Complexity: {}", complexity);
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}
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fn expand_dpad_string(s: &str) -> String {
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let sequence: Vec<usize> = s.chars().map(char_to_directional_keypad_index).collect();
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sequence_to_dpad_steps(
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&directional_keypad(),
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sequence,
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char_to_directional_keypad_index('A'),
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)
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}
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fn expand_numpad_string(s: &str) -> String {
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let sequence: Vec<usize> = s.chars().map(char_to_numerical_keypad_index).collect();
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sequence_to_dpad_steps(
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&numerical_keypad(),
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sequence,
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char_to_numerical_keypad_index('A'),
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)
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}
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fn sequence_to_dpad_steps(keypad: &Keypad, sequence: Vec<usize>, start: usize) -> String {
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let mut sequence = sequence.clone();
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sequence.insert(0, start);
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let mut total_path = "".to_string();
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for w in sequence.windows(2) {
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let best_path = shortest_paths(keypad, w[0], w[1])
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.into_iter()
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// convert paths to strings
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.map(|path| path.iter().map(direction_to_char).collect::<String>())
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// get the most efficient path (there are certain arbitrary rules for efficiency)
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.max_by_key(|path| efficiency_score(path.as_str()))
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.unwrap();
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total_path.push_str(&best_path);
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total_path.push_str("A");
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}
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total_path
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}
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fn shortest_paths(keypad: &Keypad, start: usize, end: usize) -> Vec<Vec<Direction>> {
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fn path_costs(keypad: &Keypad, p: usize, cost_so_far: u64, costs: &mut HashMap<usize, u64>) {
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if cost_so_far < costs.get(&p).copied().unwrap_or(u64::MAX) {
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costs.insert(p, cost_so_far);
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} else {
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return;
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}
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for &adjacent in keypad.adjacents(p) {
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path_costs(keypad, adjacent, cost_so_far + 1, costs);
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}
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}
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let mut costs: HashMap<usize, u64> = HashMap::new();
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path_costs(keypad, end, 0, &mut costs);
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fn find_paths(
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keypad: &Keypad,
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start: usize,
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costs: &HashMap<usize, u64>,
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) -> Vec<Vec<Direction>> {
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if costs[&start] == 0 {
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return vec![vec![]];
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}
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keypad.buttons[start]
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.links
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.iter()
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.filter(|(_, adjacent)| costs[adjacent] < costs[&start])
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.flat_map(|(&direction, &adjacent)| {
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let mut paths = find_paths(keypad, adjacent, costs);
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paths.iter_mut().for_each(|path| {
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path.insert(0, direction);
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});
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paths
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})
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.collect()
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}
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find_paths(keypad, start, &costs)
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}
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fn efficiency_score(s: &str) -> u64 {
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let repetition_score = s
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.chars()
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.collect::<Vec<char>>()
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.windows(2)
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.filter(|w| w[0] == w[1])
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.count() as u64;
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let mut order_mishaps: u64 = 0;
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for ss in s.split("A") {
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order_mishaps += ss.matches(">v").count() as u64;
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order_mishaps += ss.matches("^<").count() as u64;
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order_mishaps += ss.matches("v<").count() as u64;
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order_mishaps += ss.matches(">^").count() as u64;
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}
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(repetition_score << 32) | (u32::MAX as u64 - order_mishaps)
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}
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struct Keypad {
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buttons: Vec<Button>,
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}
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impl Keypad {
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fn adjacents(&self, button: usize) -> impl Iterator<Item = &usize> {
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self.buttons[button].links.values()
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}
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}
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#[derive(Default, Clone)]
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struct Button {
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links: HashMap<Direction, usize>,
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}
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fn char_to_numerical_keypad_index(c: char) -> usize {
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match c {
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'7' => 0,
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'8' => 1,
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'9' => 2,
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'4' => 3,
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'5' => 4,
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'6' => 5,
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'1' => 6,
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'2' => 7,
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'3' => 8,
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'0' => 9,
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'A' => 10,
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_ => panic!("The given char {c} has no place on a numerical keypad."),
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}
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}
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fn char_to_directional_keypad_index(c: char) -> usize {
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match c {
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'^' => 0,
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'A' => 1,
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'<' => 2,
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'v' => 3,
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'>' => 4,
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_ => panic!("The given char {c} has no place on a directional keypad."),
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}
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}
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fn numerical_keypad() -> Keypad {
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let mut buttons = vec![Button::default(); 11];
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// 7
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buttons[0].links.insert(Direction::East, 1);
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buttons[0].links.insert(Direction::South, 3);
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// 8
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buttons[1].links.insert(Direction::West, 0);
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buttons[1].links.insert(Direction::East, 2);
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buttons[1].links.insert(Direction::South, 4);
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// 9
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buttons[2].links.insert(Direction::West, 1);
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buttons[2].links.insert(Direction::South, 5);
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// 4
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buttons[3].links.insert(Direction::East, 4);
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buttons[3].links.insert(Direction::North, 0);
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buttons[3].links.insert(Direction::South, 6);
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// 5
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buttons[4].links.insert(Direction::West, 3);
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buttons[4].links.insert(Direction::East, 5);
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buttons[4].links.insert(Direction::South, 7);
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buttons[4].links.insert(Direction::North, 1);
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// 6
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buttons[5].links.insert(Direction::West, 4);
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buttons[5].links.insert(Direction::South, 8);
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buttons[5].links.insert(Direction::North, 2);
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// 1
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buttons[6].links.insert(Direction::North, 3);
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buttons[6].links.insert(Direction::East, 7);
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// 2
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buttons[7].links.insert(Direction::West, 6);
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buttons[7].links.insert(Direction::East, 8);
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buttons[7].links.insert(Direction::North, 4);
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buttons[7].links.insert(Direction::South, 9);
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// 3
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buttons[8].links.insert(Direction::North, 5);
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buttons[8].links.insert(Direction::West, 7);
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buttons[8].links.insert(Direction::South, 10);
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// 0
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buttons[9].links.insert(Direction::North, 7);
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buttons[9].links.insert(Direction::East, 10);
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// A
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buttons[10].links.insert(Direction::West, 9);
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buttons[10].links.insert(Direction::North, 8);
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Keypad { buttons }
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}
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fn directional_keypad() -> Keypad {
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let mut buttons = vec![Button::default(); 5];
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// ^
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buttons[0].links.insert(Direction::East, 1);
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buttons[0].links.insert(Direction::South, 3);
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// A
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buttons[1].links.insert(Direction::West, 0);
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buttons[1].links.insert(Direction::South, 4);
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// <
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buttons[2].links.insert(Direction::East, 3);
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// v
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buttons[3].links.insert(Direction::East, 4);
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buttons[3].links.insert(Direction::North, 0);
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buttons[3].links.insert(Direction::West, 2);
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// >
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buttons[4].links.insert(Direction::North, 1);
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buttons[4].links.insert(Direction::West, 3);
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Keypad { buttons }
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}
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fn direction_to_char(direction: &Direction) -> char {
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match direction {
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Direction::North => '^',
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Direction::South => 'v',
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Direction::West => '<',
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Direction::East => '>',
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}
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}
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@ -24,7 +24,9 @@ mod day18;
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mod day19;
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#[allow(dead_code)]
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mod day2;
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#[allow(dead_code)]
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mod day20;
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mod day21;
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#[allow(dead_code)]
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mod day3;
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#[allow(dead_code)]
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@ -41,7 +43,7 @@ mod day8;
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mod day9;
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fn main() {
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day20::day20();
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day21::day21();
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}
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pub fn input(day: u8) -> String {
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@ -1,4 +1,4 @@
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use std::{fmt::Display, intrinsics::atomic_cxchgweak_acquire_acquire};
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use std::fmt::Display;
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use itertools::Itertools;
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