42 lines
1.0 KiB
Rust
42 lines
1.0 KiB
Rust
pub fn day6() {
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// let input = "3,4,3,1,2";
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let input = include_str!("../input/day6.txt");
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let initial_fishes = input
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.trim()
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.split(",")
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.map(|s| s.parse::<usize>().unwrap())
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.collect::<Vec<_>>();
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count_fishes_after(&initial_fishes, 18);
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count_fishes_after(&initial_fishes, 80);
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count_fishes_after(&initial_fishes, 256);
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}
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fn count_fishes_after(initial_fishes: &[usize], days: u32) {
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let mut fish_batches = [0_u64; 9];
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for f in initial_fishes {
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fish_batches[*f] += 1;
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}
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for _ in 1..=days {
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let old_batches = fish_batches;
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fish_batches = [0; 9];
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for counter in 0..=7 {
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fish_batches[counter] = old_batches[counter + 1];
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}
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// each fish previously at 0 spawns a new fish with counter 8 and resets its counter to 6
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fish_batches[8] = old_batches[0];
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fish_batches[6] += old_batches[0];
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}
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println!(
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"total fishes after {} days: {}",
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days,
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fish_batches.iter().sum::<u64>()
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);
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}
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