65 lines
1.9 KiB
Rust
65 lines
1.9 KiB
Rust
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#![feature(const_str_split_at)]
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use std::collections::{HashMap, HashSet};
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const INPUT_LINES: usize = {
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let bytes = include_bytes!("input.txt");
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let mut i = 0;
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let mut count = 0;
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while i < bytes.len() {
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if bytes[i] == b'\n' {
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count += 1;
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}
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i += 1;
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}
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count
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};
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const INPUT: [u64; INPUT_LINES] = {
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let data = include_str!("input.txt");
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let mut nums = [0; INPUT_LINES];
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let mut i = 0;
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let mut count = 0;
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let mut last_newline = 0;
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while i < data.len() {
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if data.as_bytes()[i] == b'\n' {
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let Ok(parsed) = u64::from_str_radix(data.split_at(last_newline).1.split_at(i - last_newline).0.trim_ascii(), 10) else {
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panic!();
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};
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nums[count] = parsed;
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count += 1;
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last_newline = i;
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}
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i += 1;
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}
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nums
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};
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fn main() {
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let mut sequences = HashMap::<[i8; 4], u64>::new();
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for mut secret in INPUT {
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let mut sequence: [i8; 4] = [0, 0, 0, 0];
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let mut used = HashSet::<[i8; 4]>::new();
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for i in 0..2000 {
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let last_bananas: i8 = (secret % 10).try_into().unwrap();
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secret ^= secret * 64;
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secret %= 16777216;
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secret ^= secret / 32;
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secret %= 16777216;
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secret ^= secret * 2048;
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secret %= 16777216;
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sequence[0] = sequence[1];
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sequence[1] = sequence[2];
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sequence[2] = sequence[3];
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sequence[3] = TryInto::<i8>::try_into(secret % 10).unwrap() - last_bananas;
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if i < 4 || used.contains(&sequence) { continue } // Skip first 4 numbers, they can never form a real sequence
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*sequences.entry(sequence).or_default() += secret % 10;
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used.insert(sequence);
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}
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}
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println!("Result: {}", sequences.values().max().unwrap());
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}
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