it's ugly but it works

2021/src/day18.rs

@@ -91,14 +91,10 @@ fn explode(node: &mut Node, depth: usize) -> Option<(u8, u8)> {
     if let Leaf(_) = node {return None;}
 
     if depth >= 4 {
-        let (left, right) = node.unwrap_branch();
-        match (left, right) {
-            (Leaf(v1), Leaf(v2)) => {
+        if let (Leaf(v1), Leaf(v2)) = node.unwrap_branch() {
             let result = (*v1, *v2);
             *node = Leaf(0);
             return Some(result);
-            },
-            _ => (),
         }
     }
 

2022/Cargo.toml

@@ -23,6 +23,11 @@ path = "src/day3.rs"
 name = "day4"
 path = "src/day4.rs"
 
+[[bin]]
+name = "day5"
+path = "src/day5.rs"
+
+
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]

2022/src/day5.rs

@@ -1,29 +1,113 @@
-const DATA: &'static str = "
-    [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
-";
+use core::num::ParseIntError;
 
 
+const DATA: &'static str = include_str!("../data/day5.txt");
+// const DATA: &'static str = "
+//     [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
+// ";
+
+
+enum BadLine {
+    NotEnoughWords,
+    ParseError(ParseIntError),
+}
+
+
+#[derive(Debug)]
 struct State {
-    stacks: Vec<Vec<char>>,
+    stacks: [Vec<char>; 9],
 }
 
-impl std::str::FromStr for State {
-    fn from_str(data: &str) -> State {
-        let lines: Vec<&str> = data.lines().collect();
-        let mut stacks = Vec::new(Vec::new());
+impl State {
+    fn process(&mut self, op: &Instruction) {
+        for _ in 0..(op.count) {
+            let item = self.stacks[op.src as usize - 1].pop().unwrap();
+            self.stacks[op.dst as usize - 1].push(item);
+        }
+    }
+
+    fn process_inorder(&mut self, op: &Instruction) {
+        let src_stack = &mut self.stacks[op.src as usize - 1];
+        let split_idx = src_stack.len() - op.count as usize;
+        let mut substack = src_stack.split_off(split_idx);
+        self.stacks[op.dst as usize - 1].append(&mut substack);
+    }
+
+    fn get_tops(&self) -> String {
+        let mut res = String::with_capacity(9);
+        for stack in &self.stacks {
+            res.push(*stack.last().unwrap());
+        }
+        res
+    }
+}
+
+
+#[derive(Debug)]
+struct Instruction {
+    count: u32,
+    src: u32,
+    dst: u32,
+}
+
+
+fn parse_map(map: &str) -> State {
+    let rows: Vec<&str> = map.lines().collect();
+    let mut stacks: [Vec<char>; 9] = Default::default();
     // skip the first row, because it's just the stack numbers
-        for row in lines.rev().skip(1) {
-            for (i, ident) in row.split(' ') {
-                let ident = ident.trim_matches(|c| c == '[' || c == ']');
+    for row in rows.iter().rev().skip(1) {
+        for (col_num, c) in row.chars().enumerate() {
+            if c.is_ascii_uppercase() {
+                let stack_idx = (col_num - 1) / 4;
+                stacks[stack_idx].push(c);
             }
         }
     }
+
+    State { stacks }
+}
+
+
+fn parse_instruction(data: &str) -> Result<Instruction, BadLine> {
+    let mut words = data.split(' ');
+    Ok(Instruction {
+        count: words.nth(1).ok_or(BadLine::NotEnoughWords)?.parse().map_err(|e| BadLine::ParseError(e))?,
+        src: words.nth(1).ok_or(BadLine::NotEnoughWords)?.parse().map_err(|e| BadLine::ParseError(e))?,
+        dst: words.nth(1).ok_or(BadLine::NotEnoughWords)?.parse().map_err(|e| BadLine::ParseError(e))?,
+    })
+}
+
+
+fn main() -> Result<(), String> {
+    let mut splat = DATA.trim_end().split("\n\n");
+    let map = splat.next().unwrap();
+    let instruction_lines = splat.next().unwrap();
+    let mut state = parse_map(map);
+
+    let instructions: Vec<Instruction> = instruction_lines.lines()
+        .map(|line| parse_instruction(line).map_err(|_e| format!("Bad line: {line}")))
+        .collect::<Result<Vec<Instruction>, String>>()?;
+
+    for i in &instructions {
+        state.process(i);
+    }
+
+    println!("Part 1: {}", state.get_tops());
+
+    let mut state2 = parse_map(map);
+    for i in &instructions {
+        state2.process_inorder(i);
+    }
+
+    println!("Part 2: {}", state2.get_tops());
+
+    Ok(())
 }