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day23 part 2

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This commit is contained in:
Glenn Griffin 2020-12-23 21:05:33 -08:00
parent ca51acbec6
commit 8abb183072
1 changed files with 20 additions and 6 deletions
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24
src/day23.rs
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@ -19,9 +19,9 @@ struct Cups {
} }
impl Cups { impl Cups {
fn parse(input: &[u8]) -> Option<Self> { fn parse(input: &[u8], total_len: usize) -> Option<Self> {
let mut cups = vec![Cup(0); input.len()]; let mut cups = vec![Cup(0); total_len];
let input_iter = input.iter().map(|x| x - b'0'); let input_iter = input.iter().map(|x| (x - b'0') as u32).chain(input.len() as u32 + 1 ..= total_len as u32);
for (curr, next) in input_iter.clone().zip(input_iter.cycle().skip(1)) { for (curr, next) in input_iter.clone().zip(input_iter.cycle().skip(1)) {
cups[curr as usize - 1] = Cup(next as u32); cups[curr as usize - 1] = Cup(next as u32);
} }
@ -37,7 +37,8 @@ impl Cups {
let taken_2 = self.next_cup(taken_1); let taken_2 = self.next_cup(taken_1);
let taken_3 = self.next_cup(taken_2); let taken_3 = self.next_cup(taken_2);
let mut dest_cup = Cup::from_idx((self.current.as_idx() + self.cups.len() - 1) % self.cups.len()); let mut dest_cup =
Cup::from_idx((self.current.as_idx() + self.cups.len() - 1) % self.cups.len());
Cup(((self.current.0 as usize - 1 + self.cups.len() - 1) % self.cups.len()) as u32 + 1); Cup(((self.current.0 as usize - 1 + self.cups.len() - 1) % self.cups.len()) as u32 + 1);
while dest_cup == taken_1 || dest_cup == taken_2 || dest_cup == taken_3 { while dest_cup == taken_1 || dest_cup == taken_2 || dest_cup == taken_3 {
dest_cup = Cup::from_idx((dest_cup.as_idx() + self.cups.len() - 1) % self.cups.len()); dest_cup = Cup::from_idx((dest_cup.as_idx() + self.cups.len() - 1) % self.cups.len());
@ -61,7 +62,7 @@ impl Cups {
#[aoc(day23, part1)] #[aoc(day23, part1)]
fn solve_d23_p1(input: &[u8]) -> usize { fn solve_d23_p1(input: &[u8]) -> usize {
let mut cups = Cups::parse(input).unwrap(); let mut cups = Cups::parse(input, input.len()).unwrap();
for _ in 0..100 { for _ in 0..100 {
cups.do_move(); cups.do_move();
} }
@ -70,3 +71,16 @@ fn solve_d23_p1(input: &[u8]) -> usize {
.take_while(|&cup| cup != Cup(1)) .take_while(|&cup| cup != Cup(1))
.fold(0, |accum, cup| accum * 10 + cup.0 as usize) .fold(0, |accum, cup| accum * 10 + cup.0 as usize)
} }
#[aoc(day23, part2)]
fn solve_d23_p2(input: &[u8]) -> usize {
let mut cups = Cups::parse(input, 1_000_000).unwrap();
for _ in 0..10_000_000 {
cups.do_move();
}
cups.iter(Cup(1))
.skip(1)
.take(2)
.map(|x| x.0 as usize)
.product()
}