Solve year 2022 day 05

src/year2022/day05.rs

@@ -1,11 +1,9 @@
-use std::collections::BTreeMap;
-
 use crate::util::parse::ParseExt;
 
-fn parse(input: &str) -> (BTreeMap<usize, Vec<char>>, Vec<[u32; 3]>) {
-    let mut crates: BTreeMap<usize, Vec<char>> = BTreeMap::new();
-    let mut moves = vec![];
-    let (board, moveset) = input.split_once("\n\n\n").expect("must be there");
+fn parse(input: &str) -> Option<(Vec<Vec<char>>, impl Iterator<Item = [u32; 3]> + '_)> {
+    let (board, moveset) = input.split_once("\n\n")?;
+    let size = board.lines().last()?.u32s().count();
+    let mut crates: Vec<Vec<char>> = vec![vec![]; size + 1];
 
     board.lines().for_each(|line| {
         if !line.contains('[') {
@@ -16,35 +14,66 @@ fn parse(input: &str) -> (BTreeMap<usize, Vec<char>>, Vec<[u32; 3]>) {
             .enumerate()
             .filter(|(_idx, c)| c.is_ascii_uppercase())
             .for_each(|(idx, c)| {
-                crates
-                    .entry(((idx - 4) / 4) + 1)
-                    .and_modify(|v| v.push(c))
-                    .or_insert(vec![]);
+                crates[((idx + 2) / 4) + 1].push(c);
             });
     });
-    crates.values_mut().for_each(|v| v.reverse());
+    for v in crates.iter_mut() {
+        v.reverse();
+    }
 
-    let moves = moveset
-        .lines()
-        .map(|line| {
-            let mut nums = line.u32s();
-            [
-                nums.next().expect("first num"),
-                nums.next().expect("second num"),
-                nums.next().expect("third num"),
-            ]
-        })
-        .collect();
+    let moves = moveset.lines().filter_map(|line| {
+        let mut nums = line.u32s();
+        Some([nums.next()?, nums.next()?, nums.next()?])
+    });
 
-    (crates, moves)
+    Some((crates, moves))
 }
 
 pub fn part1(input: &str) -> impl std::fmt::Display {
-    ""
+    let (mut crates, moves) = parse(input).expect("parsing failed");
+    let mut out: Vec<String> = vec![String::new(); crates.len()];
+
+    for m in moves {
+        let mut items = {
+            let mut items = Vec::with_capacity(m[0] as usize);
+            let from: &mut Vec<char> = crates[m[1] as usize].as_mut();
+            for _ in 0..m[0] {
+                items.push(from.pop().expect("AOC please don't hate us"));
+            }
+            items
+        };
+        crates[m[2] as usize].append(&mut items);
+    }
+
+    for v in crates.iter_mut().skip(1) {
+        out.push(v.pop().expect("yes").to_string());
+    }
+
+    out.join("")
 }
 
 pub fn part2(input: &str) -> impl std::fmt::Display {
-    ""
+    let (mut crates, moves) = parse(input).expect("parsing failed");
+    let mut out: Vec<String> = vec![String::new(); crates.len()];
+
+    for m in moves {
+        let mut items = {
+            let mut items = Vec::with_capacity(m[0] as usize);
+            let from: &mut Vec<char> = crates[m[1] as usize].as_mut();
+            for _ in 0..m[0] {
+                items.push(from.pop().expect("AOC please don't hate us"));
+            }
+            items.reverse();
+            items
+        };
+        crates[m[2] as usize].append(&mut items);
+    }
+
+    for v in crates.iter_mut().skip(1) {
+        out.push(v.pop().expect("yes").to_string());
+    }
+
+    out.join("")
 }
 
 #[test]