Day 9 shenanigans

src/day9/mod.rs

@@ -0,0 +1,94 @@
+use std::collections::HashMap;
+
+use crate::utils::Day;
+
+#[derive(Debug, Default)]
+pub struct Day9 {
+    pub input: String,
+}
+
+impl Day for Day9 {
+    fn part1(&mut self) -> String {
+        let sequences = self.input.lines().map(|l| l.split_ascii_whitespace().map(|n| n.parse::<isize>().unwrap()).collect::<Vec<_>>());
+        let mut acc = 0i128;
+
+        for sequence in sequences {
+            let mut i = 1usize;
+            let len = sequence.len();
+            let mut sequence_map = HashMap::<usize, Vec::<isize>>::new();
+
+            sequence_map.insert(0, sequence.into_iter().rev().collect());
+
+            loop {
+                let mut new = Vec::<isize>::with_capacity(len-i);
+                let mut past: Option<isize> = None;
+                for num in sequence_map.get(&(i-1)).unwrap() {
+                    if let Some(past_unwrapped) = past {
+                        new.push(past_unwrapped - num);
+                    }
+                    past = Some(*num);
+                }
+
+                let done = new.iter().all(|n| n == &0);
+                if done { new.push(0); }
+                sequence_map.insert(i, new);
+
+                if done { break }
+                else { i += 1; }
+            }
+
+            for j in (0..=i).rev() {
+                let diff = *sequence_map.get(&j).unwrap().first().unwrap();
+                let Some(modify_arr) = sequence_map.get_mut(&(j-1)) else { break };
+
+                modify_arr.insert(0, *modify_arr.first().unwrap() + diff);
+            }
+
+            acc += sequence_map[&0][0] as i128;
+        }
+
+        acc.to_string()
+    }
+
+    fn part2(&mut self) -> String {
+        let sequences = self.input.lines().map(|l| l.split_ascii_whitespace().map(|n| n.parse::<isize>().unwrap()).collect::<Vec<_>>());
+        let mut acc = 0i128;
+
+        for sequence in sequences {
+            let mut i = 1usize;
+            let len = sequence.len();
+            let mut sequence_map = HashMap::<usize, Vec::<isize>>::new();
+
+            sequence_map.insert(0, sequence.into_iter().rev().collect());
+
+            loop {
+                let mut new = Vec::<isize>::with_capacity(len-i);
+                let mut past: Option<isize> = None;
+                for num in sequence_map.get(&(i-1)).unwrap() {
+                    if let Some(past_unwrapped) = past {
+                        new.push(past_unwrapped - num);
+                    }
+                    past = Some(*num);
+                }
+
+                let done = new.iter().all(|n| n == &0);
+                if done { new.push(0); }
+                sequence_map.insert(i, new);
+
+                if done { break }
+                else { i += 1; }
+            }
+
+            for j in (0..=i).rev() {
+                let diff = *sequence_map.get(&j).unwrap().last().unwrap();
+                let Some(modify_arr) = sequence_map.get_mut(&(j-1)) else { break };
+
+                modify_arr.push(*modify_arr.last().unwrap() - diff);
+            }
+
+            acc += *sequence_map[&0].last().unwrap() as i128;
+        }
+
+        acc.to_string()
+    }
+}

src/main.rs

@@ -7,7 +7,7 @@ use std::{
 use clap::{Parser, Subcommand, ValueEnum};
 
 use crate::{
-    day1::Day1, day2::Day2, day3::Day3, day4::Day4, day5::Day5, day6::Day6, day7::Day7, day8::Day8, utils::Day,
+    day1::Day1, day2::Day2, day3::Day3, day4::Day4, day5::Day5, day6::Day6, day7::Day7, day8::Day8, day9::Day9, utils::Day,
 };
 
 pub mod day1;
@@ -18,6 +18,7 @@ pub mod day5;
 pub mod day6;
 pub mod day7;
 pub mod day8;
+pub mod day9;
 pub mod fetcher;
 pub mod utils;
 
@@ -118,6 +119,7 @@ async fn main() {
                     hands: vec![],
                 }),
                 8 => Box::new(Day8 { input }),
+                9 => Box::new(Day9 { input }),
                 _ => panic!("Invalid day #"),
             };
             let start = std::time::Instant::now();
@@ -177,6 +179,7 @@ async fn main() {
                     hands: vec![],
                 }),
                 8 => Box::new(Day8 { input }),
+                9 => Box::new(Day9 { input }),
                 _ => panic!("Invalid day #"),
             };
             let mut timings = Vec::<Duration>::new();