103 lines
2.9 KiB
Rust
103 lines
2.9 KiB
Rust
use std::io::{self, BufRead};
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fn apply(deck: &mut Vec<usize>, operation: &str) {
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let words: Vec<_> = operation.split(' ').collect();
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match words[0] {
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"cut" => {
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let offset: isize = words[1].parse().expect("Not a valid number for cutting");
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if offset < 0 {
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let offset = deck.len() - (offset.abs()) as usize;
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let cut: Vec<_> = deck.drain(0..offset).collect();
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cut.into_iter().for_each(|n| deck.push(n));
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} else {
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let clone = deck.clone();
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let (left, right) = clone.split_at(offset as usize);
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*deck = right.to_vec();
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deck.append(&mut left.to_vec());
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}
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}
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// deal
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"deal" => match words[1] {
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// with increment
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"with" => {
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let length = deck.len();
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let increment: usize = words[3].parse().unwrap();
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let old_deck = deck.clone();
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for i in 0..length {
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deck[(i * increment) % length] = old_deck[i];
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}
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}
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// into new stack
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"into" => deck.reverse(),
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_ => unreachable!("Unknown deal command"),
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},
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_ => unreachable!("Unknown shuffle command"),
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};
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}
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fn create_deck(len: usize) -> Vec<usize> {
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let mut deck = Vec::with_capacity(len);
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(0..len).for_each(|n| deck.push(n));
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deck
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}
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const DECK_SIZE: usize = 10007;
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const P2_DECK_SIZE: usize = 119315717514047;
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const P2_ITERATIONS: usize = 101741582076661;
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fn main() {
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let input: Vec<_> = io::stdin().lock().lines().map(|l| l.unwrap()).collect();
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let mut deck = create_deck(DECK_SIZE);
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for command in &input {
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apply(&mut deck, command);
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}
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println!("{}", deck.iter().position(|&x| x == 2019).unwrap());
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}
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mod tests {
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use super::*;
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#[test]
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fn deal_test() {
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let mut deck = create_deck(10);
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let instructions = "deal with increment 7
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deal into new stack
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deal into new stack";
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for line in instructions.lines() {
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apply(&mut deck, line);
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}
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assert_eq!(deck, &[0, 3, 6, 9, 2, 5, 8, 1, 4, 7]);
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}
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#[test]
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fn cut_deal_test() {
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let mut deck = create_deck(10);
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let instructions = "cut 6
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deal with increment 7
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deal into new stack";
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for line in instructions.lines() {
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apply(&mut deck, line);
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}
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assert_eq!(deck, &[3, 0, 7, 4, 1, 8, 5, 2, 9, 6]);
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}
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#[test]
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fn test_all() {
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let mut deck = create_deck(10);
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let instructions = "deal into new stack
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cut -2
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deal with increment 7
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cut 8
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cut -4
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deal with increment 7
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cut 3
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deal with increment 9
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deal with increment 3
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cut -1";
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for line in instructions.lines() {
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apply(&mut deck, line);
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}
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assert_eq!(deck, &[9, 2, 5, 8, 1, 4, 7, 0, 3, 6]);
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}
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}
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