- commit
- 791c7e1cb91b5745f234173dfb46eff7edb7d703
- parent
- 4014abd9f483824f746823514973eb85f3072fef
- Author
- Tobias Bengfort <tobias.bengfort@posteo.de>
- Date
- 2021-12-21 09:26
day 21
Diffstat
| A | 2021/21/input.txt | 2 | ++ |
| A | 2021/21/part1.rs | 57 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| A | 2021/21/part2.rs | 111 | ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| A | 2021/21/test.txt | 2 | ++ |
4 files changed, 172 insertions, 0 deletions
diff --git a/2021/21/input.txt b/2021/21/input.txt
@@ -0,0 +1,2 @@ -1 1 Player 1 starting position: 9 -1 2 Player 2 starting position: 3
diff --git a/2021/21/part1.rs b/2021/21/part1.rs
@@ -0,0 +1,57 @@
-1 1 use std::env::args;
-1 2 use std::fs::File;
-1 3 use std::io::BufRead;
-1 4 use std::io::BufReader;
-1 5
-1 6 fn get_data() -> (u64, u64) {
-1 7 let path = args().nth(1).unwrap();
-1 8 let file = File::open(path).unwrap();
-1 9
-1 10 let mut state = 0;
-1 11 let mut player1 = 0;
-1 12 let mut player2 = 0;
-1 13
-1 14 for line in BufReader::new(file).lines() {
-1 15 match state {
-1 16 0 => {
-1 17 player1 = line.unwrap()[28..].parse::<u64>().unwrap();
-1 18 state = 1;
-1 19 },
-1 20 1 => {
-1 21 player2 = line.unwrap()[28..].parse::<u64>().unwrap();
-1 22 state = 2;
-1 23 },
-1 24 _ => unreachable!(),
-1 25 }
-1 26 }
-1 27
-1 28 return (player1, player2);
-1 29 }
-1 30
-1 31 fn main() {
-1 32 let (mut player1, mut player2) = get_data();
-1 33
-1 34 let mut die: u64 = 0;
-1 35 let mut score1: u64 = 0;
-1 36 let mut score2: u64 = 0;
-1 37
-1 38 loop {
-1 39 let d1 = 3 * (die % 100) + 6;
-1 40 player1 = (player1 + d1 - 1) % 10 + 1;
-1 41 score1 += player1;
-1 42 die += 3;
-1 43 if score1 >= 1000 {
-1 44 println!("{}", score2 * die);
-1 45 break;
-1 46 }
-1 47
-1 48 let d2 = 3 * (die % 100) + 6;
-1 49 player2 = (player2 + d2 - 1) % 10 + 1;
-1 50 score2 += player2;
-1 51 die += 3;
-1 52 if score2 >= 1000 {
-1 53 println!("{}", score1 * die);
-1 54 break;
-1 55 }
-1 56 }
-1 57 }
diff --git a/2021/21/part2.rs b/2021/21/part2.rs
@@ -0,0 +1,111 @@
-1 1 use std::env::args;
-1 2 use std::fs::File;
-1 3 use std::io::BufRead;
-1 4 use std::io::BufReader;
-1 5
-1 6 const TURNS: usize = 11;
-1 7
-1 8 fn get_data() -> (usize, usize) {
-1 9 let path = args().nth(1).unwrap();
-1 10 let file = File::open(path).unwrap();
-1 11
-1 12 let mut state = 0;
-1 13 let mut player1 = 0;
-1 14 let mut player2 = 0;
-1 15
-1 16 for line in BufReader::new(file).lines() {
-1 17 match state {
-1 18 0 => {
-1 19 player1 = line.unwrap()[28..].parse::<usize>().unwrap();
-1 20 state = 1;
-1 21 },
-1 22 1 => {
-1 23 player2 = line.unwrap()[28..].parse::<usize>().unwrap();
-1 24 state = 2;
-1 25 },
-1 26 _ => unreachable!(),
-1 27 }
-1 28 }
-1 29
-1 30 return (player1 - 1, player2 - 1);
-1 31 }
-1 32
-1 33 fn index(turn: usize, score: usize, position: usize) -> usize {
-1 34 assert!(turn < TURNS);
-1 35 assert!(score < 21);
-1 36 assert!(position < 10);
-1 37
-1 38 return turn + score * TURNS + position * TURNS * 21;
-1 39 }
-1 40
-1 41 fn main() {
-1 42 let (player1, player2) = get_data();
-1 43
-1 44 let mut counts1 = [0u64; TURNS * 21 * 10];
-1 45 let mut counts2 = [0u64; TURNS * 21 * 10];
-1 46 let mut finishes1 = [0u64; TURNS];
-1 47 let mut finishes2 = [0u64; TURNS];
-1 48
-1 49 counts1[index(0, 0, player1)] += 1;
-1 50 counts2[index(0, 0, player2)] += 1;
-1 51
-1 52 for turn in 1..TURNS {
-1 53 for score in 0..21 {
-1 54 for position in 0..10 {
-1 55 if score > position {
-1 56 let i = index(turn, score, position);
-1 57 let old_score = score - (position + 1);
-1 58 for a in [1, 2, 3].iter() {
-1 59 for b in [1, 2, 3].iter() {
-1 60 for c in [1, 2, 3].iter() {
-1 61 let old_position = (position + 10 - (a + b + c)) % 10;
-1 62 let j = index(turn - 1, old_score, old_position);
-1 63 counts1[i] += counts1[j];
-1 64 counts2[i] += counts2[j];
-1 65 }
-1 66 }
-1 67 }
-1 68 }
-1 69 }
-1 70 }
-1 71
-1 72 for position in 0..10 {
-1 73 for old_score in (21 - (position + 1))..21 {
-1 74 for a in [1, 2, 3].iter() {
-1 75 for b in [1, 2, 3].iter() {
-1 76 for c in [1, 2, 3].iter() {
-1 77 let old_position = (position + 10 - (a + b + c)) % 10;
-1 78 let j = index(turn - 1, old_score, old_position);
-1 79 finishes1[turn] += counts1[j];
-1 80 finishes2[turn] += counts2[j];
-1 81 }
-1 82 }
-1 83 }
-1 84 }
-1 85 }
-1 86 }
-1 87
-1 88 // the two players can play their games independently and just
-1 89 // multiply their universes in the end
-1 90 let mut open1: u64 = 1;
-1 91 let mut wins1: u64 = 0;
-1 92
-1 93 let mut open2: u64 = 1;
-1 94 let mut wins2: u64 = 0;
-1 95
-1 96 for turn in 1..TURNS {
-1 97 open1 *= 27;
-1 98 open1 -= finishes1[turn];
-1 99 wins1 += finishes1[turn] * open2;
-1 100
-1 101 open2 *= 27;
-1 102 open2 -= finishes2[turn];
-1 103 wins2 += finishes2[turn] * open1;
-1 104 }
-1 105
-1 106 if wins1 > wins2 {
-1 107 println!("{}", wins1);
-1 108 } else {
-1 109 println!("{}", wins2);
-1 110 }
-1 111 }
diff --git a/2021/21/test.txt b/2021/21/test.txt
@@ -0,0 +1,2 @@ -1 1 Player 1 starting position: 4 -1 2 Player 2 starting position: 8