day 20 finished

src/days/day20/mod.rs

@@ -0,0 +1,340 @@
+use super::template::{DayTrait, ResultType};
+use crate::common::file::split_lines;
+use itertools::Itertools;
+use std::{num::ParseIntError, str::FromStr};
+use thiserror::Error;
+
+const DAY_NUMBER: usize = 20;
+
+pub struct Day;
+
+impl DayTrait for Day {
+    fn get_day_number(&self) -> usize {
+        DAY_NUMBER
+    }
+
+    fn part1(&self, lines: &str) -> anyhow::Result<ResultType> {
+        let mut ring: Ring = lines.parse()?;
+        ring.mix(1);
+        let start = ring.index_of(0)?;
+        Ok(ResultType::Integer(
+            ring.get_item(start, 1000) + ring.get_item(start, 2000) + ring.get_item(start, 3000),
+        ))
+    }
+
+    fn part2(&self, lines: &str) -> anyhow::Result<ResultType> {
+        let mut ring: Ring = lines.parse()?;
+        ring.multiply(811589153);
+        ring.mix(10);
+        let start = ring.index_of(0)?;
+        Ok(ResultType::Integer(
+            ring.get_item(start, 1000) + ring.get_item(start, 2000) + ring.get_item(start, 3000),
+        ))
+    }
+}
+
+#[derive(Debug, Error)]
+enum RingError {
+    #[error("Parse Error")]
+    ParseError(#[from] ParseIntError),
+    #[error("Item not found {0}")]
+    ItemNotFound(i64),
+}
+
+struct Ring {
+    items: Vec<i64>,
+    next: Vec<usize>,
+    prev: Vec<usize>,
+}
+
+impl FromStr for Ring {
+    type Err = RingError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let items: Vec<_> = split_lines(s).map(|line| line.parse()).try_collect()?;
+        Ok(Ring::new(items))
+    }
+}
+
+impl Ring {
+    pub fn new(items: Vec<i64>) -> Self {
+        let mut next = Vec::with_capacity(items.len());
+        for i in 1..items.len() {
+            next.push(i);
+        }
+        next.push(0);
+        let mut prev = Vec::with_capacity(items.len());
+        prev.push(items.len() - 1);
+        for i in 0..items.len() - 1 {
+            prev.push(i);
+        }
+        Self { items, next, prev }
+    }
+
+    pub fn get_item(&self, start: usize, steps: usize) -> i64 {
+        let steps = steps % self.items.len();
+        let mut next = start;
+        for _ in 0..steps {
+            next = self.next[next];
+        }
+        self.items[next]
+    }
+
+    pub fn index_of(&self, value: i64) -> Result<usize, RingError> {
+        self.items
+            .iter()
+            .position(|v| *v == value)
+            .ok_or_else(|| RingError::ItemNotFound(value))
+    }
+
+    fn next_pos(&self, pos: usize) -> usize {
+        let len = self.items.len() as i64;
+        let mut moves = self.items[pos] % (len - 1);
+        if moves > len / 2 {
+            moves -= len - 1;
+        } else if moves < -len / 2 {
+            moves += len - 1;
+        }
+
+        match moves.cmp(&0) {
+            std::cmp::Ordering::Equal => pos,
+            std::cmp::Ordering::Less => {
+                let mut prev = self.prev[pos];
+                for _ in moves..-1 {
+                    prev = self.prev[prev];
+                }
+                prev
+            }
+            std::cmp::Ordering::Greater => {
+                let mut next = self.next[pos];
+                for _ in 0..moves {
+                    next = self.next[next];
+                }
+                next
+            }
+        }
+    }
+
+    pub fn move_item(&mut self, pos: usize) {
+        let next_pos = self.next_pos(pos);
+        if next_pos == pos {
+            return;
+        }
+        let old_next = self.next[pos];
+        self.next[self.prev[pos]] = self.next[pos];
+        self.next[pos] = self.next[self.prev[next_pos]];
+        self.next[self.prev[next_pos]] = pos;
+
+        self.prev[old_next] = self.prev[pos];
+        self.prev[pos] = self.prev[next_pos];
+        self.prev[next_pos] = pos;
+    }
+
+    #[allow(dead_code)]
+    pub fn iter(&self) -> RingIter<'_> {
+        let start = self.index_of(0).unwrap_or(0);
+        RingIter::new(self, start)
+    }
+
+    fn mix(&mut self, times: usize) {
+        for _ in 0..times {
+            for pos in 0..self.items.len() {
+                self.move_item(pos);
+            }
+        }
+    }
+
+    fn multiply(&mut self, arg: i64) {
+        self.items
+            .iter_mut()
+            .for_each(|value| *value = *value * arg);
+    }
+}
+
+struct RingIter<'a> {
+    ring: &'a Ring,
+    pos: Option<usize>,
+    start: usize,
+}
+
+impl<'a> RingIter<'a> {
+    pub fn new(ring: &'a Ring, start: usize) -> Self {
+        Self {
+            ring,
+            pos: Some(start),
+            start,
+        }
+    }
+}
+
+impl Iterator for RingIter<'_> {
+    type Item = i64;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let Some(pos) = self.pos else {
+            return None;
+        };
+        let next_pos = self.ring.next[pos];
+        self.pos = if next_pos != self.start {
+            Some(next_pos)
+        } else {
+            None
+        };
+        Some(self.ring.items[pos])
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::common::file::read_string;
+    use anyhow::Result;
+
+    #[test]
+    fn test_part1() -> Result<()> {
+        let day = Day {};
+        let lines = read_string(day.get_day_number(), "example01.txt")?;
+        let expected = ResultType::Integer(3);
+        let result = day.part1(&lines)?;
+        assert_eq!(result, expected);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_part2() -> Result<()> {
+        let day = Day {};
+        let lines = read_string(day.get_day_number(), "example01.txt")?;
+        let expected = ResultType::Integer(1623178306);
+        let result = day.part2(&lines)?;
+        assert_eq!(result, expected);
+
+        Ok(())
+    }
+
+    #[test]
+    fn move1() {
+        let input = vec![1, 2, 3, 4, 5, 6, 7];
+        let mut ring = Ring::new(input);
+        let expected = vec![1, 3, 4, 5, 6, 7, 2];
+        ring.move_item(0);
+        assert_eq!(ring.iter().collect_vec(), expected);
+    }
+
+    #[test]
+    fn move7() {
+        let input = vec![7, 2, 3, 4, 5, 6, 7];
+        let mut ring = Ring::new(input);
+        let expected = vec![7, 3, 4, 5, 6, 7, 2];
+        ring.move_item(0);
+        assert_eq!(ring.iter().collect_vec(), expected);
+    }
+
+    #[test]
+    fn move2() {
+        let input = vec![1, 2, 3, 4, 5, 6, 7];
+        let mut ring = Ring::new(input);
+        let expected = vec![1, 3, 4, 2, 5, 6, 7];
+        ring.move_item(1);
+        assert_eq!(ring.iter().collect_vec(), expected);
+    }
+
+    #[test]
+    fn move_6() {
+        let input = vec![6, -2, 5, 6, 7, 8, 9];
+        let mut ring = Ring::new(input);
+        let expected = vec![6, -2, 5, 6, 7, 8, 9];
+        ring.move_item(0);
+        assert_eq!(ring.iter().collect_vec(), expected);
+    }
+
+    #[test]
+    fn move_minus1() {
+        let input = vec![4, -1, 5, 6, 7, 8, 9];
+        let mut ring = Ring::new(input);
+        let expected = vec![4, 5, 6, 7, 8, 9, -1];
+        ring.move_item(1);
+        assert_eq!(ring.iter().collect_vec(), expected);
+    }
+
+    #[test]
+    fn move_minus2() {
+        let input = vec![4, -2, 5, 6, 7, 8, 9];
+        let mut ring = Ring::new(input);
+        let expected = vec![4, 5, 6, 7, 8, -2, 9];
+        ring.move_item(1);
+        assert_eq!(ring.iter().collect_vec(), expected);
+    }
+
+    #[test]
+    fn move_minus4() {
+        let input = vec![4, -4, 5, 6, 7, 8, 9];
+        let mut ring = Ring::new(input);
+        let expected = vec![4, 5, 6, -4, 7, 8, 9];
+        ring.move_item(1);
+        assert_eq!(ring.iter().collect_vec(), expected);
+    }
+
+    #[test]
+    fn mix() {
+        let input = vec![1, 2, -3, 3, -2, 0, 4];
+        let mut ring = Ring::new(input);
+        let expected = vec![0, 3, -2, 1, 2, -3, 4];
+        ring.mix(1);
+        assert_eq!(ring.iter().collect_vec(), expected);
+    }
+
+    #[test]
+    fn get_item() {
+        let input = vec![1, 2, 3, 4, 5, 6, 7];
+        let ring = Ring::new(input);
+        assert_eq!(ring.get_item(0, 0), 1);
+        assert_eq!(ring.get_item(0, 6), 7);
+        assert_eq!(ring.get_item(0, 7), 1);
+    }
+
+    #[test]
+    fn for_part1() -> Result<()> {
+        let day = Day {};
+        let lines = read_string(day.get_day_number(), "example01.txt")?;
+        let mut ring: Ring = lines.parse()?;
+        ring.mix(1);
+        let expected = vec![0, 3, -2, 1, 2, -3, 4];
+        assert_eq!(ring.iter().collect_vec(), expected);
+
+        let start = ring.index_of(0)?;
+        assert_eq!(ring.get_item(start, 0), 0);
+        assert_eq!(ring.get_item(start, 1000), 4);
+        assert_eq!(ring.get_item(start, 2000), -3);
+        assert_eq!(ring.get_item(start, 3000), 2);
+
+        Ok(())
+    }
+
+    #[test]
+    fn for_part2() -> Result<()> {
+        let day = Day {};
+        let lines = read_string(day.get_day_number(), "example01.txt")?;
+        let mut ring: Ring = lines.parse()?;
+        ring.multiply(811589153);
+        ring.mix(10);
+        let expected = vec![
+            0,
+            -2434767459,
+            1623178306,
+            3246356612,
+            -1623178306,
+            2434767459,
+            811589153,
+        ];
+        assert_eq!(ring.iter().collect_vec(), expected);
+
+        let start = ring.index_of(0)?;
+        assert_eq!(ring.get_item(start, 0), 0);
+        assert_eq!(ring.get_item(start, 1000), 811589153);
+        assert_eq!(ring.get_item(start, 2000), 2434767459);
+        assert_eq!(ring.get_item(start, 3000), -1623178306);
+
+        Ok(())
+    }
+}

src/days/mod.rs

@@ -17,6 +17,7 @@ mod day16;
 mod day17;
 mod day18;
 mod day19;
+mod day20;
 mod template;
 
 pub use template::DayTrait;
@@ -26,7 +27,7 @@ pub mod day_provider {
     use super::*;
     use thiserror::Error;
 
-    const MAX_DAY: usize = 19;
+    const MAX_DAY: usize = 20;
 
     pub fn get_day(day_num: usize) -> Result<Box<dyn DayTrait>, ProviderError> {
         match day_num {
@@ -49,6 +50,7 @@ pub mod day_provider {
             17 => Ok(Box::new(day17::Day)),
             18 => Ok(Box::new(day18::Day)),
             19 => Ok(Box::new(day19::Day)),
+            20 => Ok(Box::new(day20::Day)),
             _ => Err(ProviderError::InvalidNumber(day_num)),
         }
     }

src/main.rs

@@ -1,3 +1,5 @@
+#![feature(get_many_mut)]
+
 mod common;
 mod days;
 mod macros;