adventofcode/days/2024/11.rs

use std::collections::HashMap;

use advent_of_code::{
    numberlength,
    strings::{convert_to_array, parsenumber},
    ExtendedOption,
};
use advent_of_code_macros::include_aoc;
use num::Integer;

include_aoc!(2024, 11);

const BILLIONS: u64 = 1000_000_000;

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
struct Stone {
    number: u64,
    left: usize,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
struct MapSkip {
    newnumber_a: u64,
    newnumber_b: u64,
    skipped_steps: usize,
}

#[derive(Debug, Clone)]
struct StoneCounter {
    cache: Vec<Stone>,
    map: HashMap<u64, ExtendedOption<MapSkip>>,
    stones: u64,
    start: usize,
    stones_billions: u64,
}

impl StoneCounter {
    fn new(start_values: Vec<u64>, rounds: usize) -> StoneCounter {
        let mut cache = Vec::with_capacity(start_values.len());
        for v in start_values.iter() {
            cache.push(Stone {
                number: *v,
                left: rounds,
            });
        }
        StoneCounter {
            cache,
            map: HashMap::with_capacity(10_000),
            stones: 0,
            start: rounds,
            stones_billions: 0,
        }
    }

    fn blink(&mut self) -> u64 {
        let mut stone: Stone;
        let mut copy: Stone;
        let (mut next, mut second);
        while self.cache.len() > 0 {
            stone = self.cache.pop().unwrap();
            copy = stone.clone();
            while stone.left > 0 {
                if self.map.contains_key(&stone.number) {
                    match self.map.get(&stone.number).unwrap() {
                        ExtendedOption::None => {
                            self.stones += 1;
                            break;
                        },
                        ExtendedOption::Some(skip) => {
                            if stone.left < skip.skipped_steps {
                                stone.left = 0
                            } else {
                                stone.left -= skip.skipped_steps;
                            }
                            stone.number = skip.newnumber_a;
                            self.cache.push(Stone {
                                number: skip.newnumber_b,
                                left: stone.left,
                            });
                            continue;
                        },
                        ExtendedOption::Unset => {},
                    }
                }
                if stone.left == 1 {
                    self.map = self
                        .map
                        .iter()
                        .filter_map(|x| {
                            Some(if *x.1 == ExtendedOption::Unset {
                                (*x.0, ExtendedOption::None)
                            } else {
                                (*x.0, *x.1)
                            })
                        })
                        .collect();
                    break;
                } else {
                    self.map.insert(stone.number, ExtendedOption::Unset);
                }
                stone.left -= 1;
                (next, second) = blink(stone.number);
                match second {
                    None => {
                        self.map.insert(stone.number, ExtendedOption::Unset);
                        stone.number = next;
                    },
                    Some(sec) => {
                        self.map.insert(
                            stone.number,
                            ExtendedOption::Some(MapSkip {
                                newnumber_a: next,
                                newnumber_b: sec,
                                skipped_steps: copy.left - stone.left,
                            }),
                        );
                    },
                }
            }
        }

        self.stones_billions * BILLIONS + self.stones
    }
}

fn combine_number(p: &[u64]) -> u64 {
    let mut o = 0;
    for i in p {
        o = o * 10 + i;
    }
    o
}

fn splitnumber(i: u64) -> (u64, u64) {
    let len = numberlength(i) as usize;
    let mut array = Vec::with_capacity(len);
    let (mut quot, mut remainder);
    quot = i;
    loop {
        (quot, remainder) = quot.div_rem(&10);
        array.insert(0, remainder);
        if quot == 0 {
            break;
        }
    }
    let (a, b) = array.split_at(len / 2);
    (combine_number(a), combine_number(b))
}

fn blink(stone: u64) -> (u64, Option<u64>) {
    if stone == 0 {
        (1, None)
    } else if numberlength(stone) % 2 == 0 {
        let (stone, t) = splitnumber(stone);
        (stone, Some(t))
    } else {
        (stone * 2024, None)
    }
}

fn main() {
    let stoneline = convert_to_array::<_, _, ' '>(DATA, parsenumber);
    let mut counter = StoneCounter::new(stoneline.clone(), 25);
    let stones = counter.blink();
    debug_assert!(stones == 235850, "{} != {}", stones, 235850);
    println!("{:?} Stones after 25 blinks", stones);
    counter = StoneCounter::new(stoneline, 75);
    println!("{:?} Stones after 75 blinks", counter.blink());
}

#[cfg(test)]
mod test {

    use super::*;

    #[test]
    fn test_blink() {
        let mut res = blink(8);
        assert_eq!(res, (16192, None));
        res = blink(res.0);
        assert_eq!(res, (32772608, None));
        res = blink(res.0);
        assert_eq!(res, (3277, Some(2608)));
    }

    #[test]
    fn test_stones() {
        let testvalues = vec![
            125, 17,
        ];
        let mut counter = StoneCounter::new(testvalues.clone(), 6);
        assert_eq!(counter.blink(), 22);

        counter = StoneCounter::new(testvalues.clone(), 25);
        assert_eq!(counter.blink(), 55312);
    }
}