From 9faaad81d3e4bcc467b6f9a18559048686813280 Mon Sep 17 00:00:00 2001
From: Greg Burri <greg.burri@gmail.com>
Date: Mon, 5 Dec 2022 12:09:19 +0100
Subject: [PATCH] Day 5

---
 src/day05.rs | 111 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.rs  |  10 +++++
 2 files changed, 121 insertions(+)
 create mode 100644 src/day05.rs

diff --git a/src/day05.rs b/src/day05.rs
new file mode 100644
index 0000000..3a0f1bc
--- /dev/null
+++ b/src/day05.rs
@@ -0,0 +1,111 @@
+use std::collections::VecDeque;
+
+use regex::Regex;
+
+type Stacks = Vec<VecDeque<char>>;
+
+pub struct Move {
+    n: usize,
+    from: usize,
+    to: usize,
+}
+
+pub fn parse(s: &str) -> (Stacks, Vec<Move>) {
+    let mut stacks = Vec::new();
+    let mut lines = s.lines();
+    while let Some(line) = lines.next() {
+        let chars: Vec<char> = line.trim_end().chars().collect();
+        if chars[1] == '1' {
+            break;
+        }
+        let n = (chars.len() + 1) / 4;
+        for _ in stacks.len()..n {
+            stacks.push(VecDeque::new());
+        }
+
+        for i in 0..n {
+            let pos_char = i * 4 + 1;
+            if chars[pos_char] != ' ' {
+                stacks[i].push_front(chars[pos_char]);
+            }
+        }
+    }
+
+    lines.next(); // Drop the empty line.
+
+    let r = Regex::new(r"move (\d+) from (\d+) to (\d+)").unwrap();
+    let mut moves = Vec::new();
+    while let Some(line) = lines.next() {
+        let cap = r.captures(line).unwrap();
+        moves.push(Move { n: cap[1].parse().unwrap(), from: cap[2].parse::<usize>().unwrap() - 1, to: cap[3].parse::<usize>().unwrap() - 1 });
+    }
+
+    (stacks, moves)
+}
+
+pub fn apply_moves_by_crate_mover_9000(stacks: &mut Stacks, moves: &[Move]) {
+    for m in moves {
+        for _ in 0..m.n {
+            if let Some(c) = stacks[m.from].pop_back() {
+                stacks[m.to].push_back(c);
+            } else {
+                break;
+            }
+        }
+    }
+}
+
+pub fn apply_moves_by_crate_mover_9001(stacks: &mut Stacks, moves: &[Move]) {
+    for m in moves {
+        let from = stacks.get_mut(m.from).unwrap();
+        let mut to_move = from.split_off(from.len() - m.n);
+        stacks[m.to].append(&mut to_move);
+    }
+}
+
+pub fn get_top_as_string(stacks: &Stacks) -> String {
+    let mut result = String::new();
+    for stack in stacks {
+        if let Some(c) = stack.back() {
+            result.push(*c);
+        }
+    }
+    result
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1() {
+        let stacks_and_moves ="    [D]
+[N] [C]
+[Z] [M] [P]
+ 1   2   3
+
+move 1 from 2 to 1
+move 3 from 1 to 3
+move 2 from 2 to 1
+move 1 from 1 to 2";
+        let (mut stacks, moves) = parse(stacks_and_moves);
+        apply_moves_by_crate_mover_9000(&mut stacks, &moves);
+        assert_eq!(get_top_as_string(&stacks), "CMZ");
+    }
+
+    #[test]
+    fn part2() {
+        let stacks_and_moves ="    [D]
+[N] [C]
+[Z] [M] [P]
+ 1   2   3
+
+move 1 from 2 to 1
+move 3 from 1 to 3
+move 2 from 2 to 1
+move 1 from 1 to 2";
+        let (mut stacks, moves) = parse(stacks_and_moves);
+        apply_moves_by_crate_mover_9001(&mut stacks, &moves);
+        assert_eq!(get_top_as_string(&stacks), "MCD");
+    }
+}
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 014c31d..8fbe072 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,6 +5,7 @@ mod day01;
 mod day02;
 mod day03;
 mod day04;
+mod day05;
 
 fn day01() -> String {
     let f = fs::File::open("data/day01.input").unwrap();
@@ -30,6 +31,14 @@ fn day04() -> String {
     format!("part1: {}, part2: {}", day04::number_fully_contain(&pairs), day04::number_overlaps(&pairs))
 }
 
+fn day05() -> String {
+    let (mut stacks, moves) = day05::parse(&fs::read_to_string("data/day05.input").unwrap());
+    let mut stacks2 = stacks.clone();
+    day05::apply_moves_by_crate_mover_9000(&mut stacks, &moves);
+    day05::apply_moves_by_crate_mover_9001(&mut stacks2, &moves);
+    format!("part1: {}, part2: {}", day05::get_top_as_string(&stacks), day05::get_top_as_string(&stacks2))
+}
+
 fn format_micros(t: u128) -> String {
     if t < 10_000 {
         format!("{} μs", t)
@@ -53,6 +62,7 @@ fn main() {
         day02,
         day03,
         day04,
+        day05,
     );
 
     let args: Vec<String> = env::args().skip(1).collect();
-- 
2.45.2