day5

1 files changed, 113 insertions, 0 deletions

diff --git a/src/bin/day5.rs b/src/bin/day5.rs
new file mode 100644
index 0000000..a5e28fd
--- /dev/null
+++ b/src/bin/day5.rs
@@ -0,0 +1,113 @@
+use std::collections::VecDeque;
+use regex::Regex;
+
+static DAY: u8 = 5;
+
+fn main() {
+    let input = advent::read_lines(DAY);
+    println!("{DAY}a: {}", find_top_crates(&input));
+    println!("{DAY}b: {}", find_top_crates_9001(&input));
+}
+
+struct CrateMover {
+    instructions: Vec<Instruction>,
+    stacks: Vec<VecDeque<char>>,
+}
+
+struct Instruction {
+    amount: usize,
+    from: usize,
+    to: usize,
+}
+
+impl CrateMover {
+    fn new(input: &[String]) -> CrateMover {
+        let re_instruction = Regex::new("move ([0-9]+) from ([0-9]+) to ([0-9]+)").unwrap();
+
+        let mut instructions = Vec::new();
+        let mut stacks = Vec::new();
+        for line in input {
+            if let Some(cap) = re_instruction.captures(line) {
+                instructions.push(Instruction {
+                    amount: cap[1].parse::<usize>().unwrap(),
+                    from: cap[2].parse::<usize>().unwrap() - 1,
+                    to: cap[3].parse::<usize>().unwrap() - 1,
+                });
+            }
+
+            if line.find('[').is_some() {
+                let chars = line.chars().collect::<Vec<_>>();
+                for (index, chunk) in chars.chunks(4).enumerate() {
+                    // chunk: "[x] "
+                    let name = chunk[1];
+                    if name == ' ' {
+                        // empty position
+                        continue;
+                    }
+                    if index >= stacks.len() {
+                        stacks.resize(index + 1, VecDeque::new());
+                    }
+                    stacks[index].push_front(name);
+                }
+            }
+        }
+
+        CrateMover { stacks, instructions }
+    }
+
+    fn move_crates(&mut self) {
+        for instruction in &self.instructions {
+            for _ in 0 .. instruction.amount {
+                let name = self.stacks[instruction.from].pop_back().expect("Stack has no crate");
+                self.stacks[instruction.to].push_back(name);
+            }
+        }
+    }
+
+    fn move_crates_9001(&mut self) {
+        for instruction in &self.instructions {
+            let drain_from = self.stacks[instruction.from].len() - instruction.amount;
+            let moved_stack = self.stacks[instruction.from].drain(drain_from ..).collect::<Vec<_>>();
+            self.stacks[instruction.to].extend(moved_stack);
+        }
+    }
+}
+
+fn find_top_crates(input: &[String]) -> String {
+    let mut cratemover = CrateMover::new(input);
+    cratemover.move_crates();
+    cratemover.stacks.iter()
+                     .map(|stack| stack.back().unwrap())
+                     .collect()
+}
+
+fn find_top_crates_9001(input: &[String]) -> String {
+    let mut cratemover = CrateMover::new(input);
+    cratemover.move_crates_9001();
+    cratemover.stacks.iter()
+                     .map(|stack| stack.back().unwrap())
+                     .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = [
+            "    [D]    ".to_string(),
+            "[N] [C]    ".to_string(),
+            "[Z] [M] [P]".to_string(),
+            " 1   2   3 ".to_string(),
+            "".to_string(),
+            "move 1 from 2 to 1".to_string(),
+            "move 3 from 1 to 3".to_string(),
+            "move 2 from 2 to 1".to_string(),
+            "move 1 from 1 to 2".to_string(),
+        ];
+
+        assert_eq!(find_top_crates(&input), "CMZ");
+        assert_eq!(find_top_crates_9001(&input), "MCD");
+    }
+}