Day 5

day5/src/main.rs

@@ -1,3 +1,99 @@
-fn main() {
-    println!("Hello, world!");
+use std::{fs::read_to_string, str::Lines};
+
+use color_eyre::Result;
+use itertools::Itertools;
+
+fn parse_stacks(input: &mut Lines) -> Vec<Vec<char>> {
+    let horizontal_stack = input
+        .map(|line| {
+            line.chars()
+                .skip(1)
+                .step_by(4)
+                .map(|c| if c.is_whitespace() { None } else { Some(c) })
+                .collect::<Vec<_>>()
+        })
+        .take_while(|line| line.first().unwrap_or(&None) != &Some('1'))
+        .collect::<Vec<_>>();
+    let num_stacks = horizontal_stack.last().map(|v| v.len()).unwrap_or(0);
+    let mut vertical_stack: Vec<Vec<char>> = Vec::with_capacity(num_stacks);
+    for _ in 0..num_stacks {
+        vertical_stack.push(vec![]);
+    }
+
+    for v in horizontal_stack.iter().rev() {
+        for (i, c) in v.iter().enumerate() {
+            if let Some(ch) = c {
+                vertical_stack[i].push(*ch);
+            }
+        }
+    }
+    vertical_stack
+}
+
+#[derive(Debug, Clone, Copy)]
+struct Move {
+    pub amount: usize,
+    pub from: usize,
+    pub to: usize,
+}
+
+impl Move {
+    fn play9000(&self, stacks: &mut [Vec<char>]) {
+        for _ in 0..self.amount {
+            if let Some(element) = stacks[self.from].pop() {
+                stacks[self.to].push(element);
+            }
+        }
+    }
+
+    fn play9001(&self, stacks: &mut [Vec<char>]) {
+        let i = stacks[self.from].len() - self.amount;
+        let mut moving = stacks[self.from].split_off(i);
+        stacks[self.to].append(&mut moving);
+    }
+}
+
+fn parse_move(line: &str) -> Move {
+    let (amount, from, to) = line
+        .split_whitespace()
+        .skip(1)
+        .step_by(2)
+        .map(|s| s.parse::<usize>().unwrap_or(0))
+        .take(3)
+        .collect_tuple()
+        .unwrap_or((0, 0, 0));
+    Move {
+        amount,
+        from: from - 1,
+        to: to - 1,
+    }
+}
+
+fn main() -> Result<()> {
+    let input = read_to_string("input.txt")?;
+    let mut lines = input.lines();
+    let mut stacks9000 = parse_stacks(&mut lines);
+    let mut stacks9001 = stacks9000.clone();
+    let moves = lines.skip(1).map(parse_move);
+    for m in moves {
+        m.play9000(&mut stacks9000);
+        m.play9001(&mut stacks9001);
+    }
+    let top9000 = stacks9000
+        .iter()
+        .map(|stack| stack.last().unwrap_or(&' '))
+        .fold(String::new(), |mut s, v| {
+            s.push(*v);
+            s
+        });
+    let top9001 = stacks9001
+        .iter()
+        .map(|stack| stack.last().unwrap_or(&' '))
+        .fold(String::new(), |mut s, v| {
+            s.push(*v);
+            s
+        });
+    println!("top crates 9000: {top9000}");
+    println!("top crates 9001: {top9001}");
+    Ok(())
 }