Day05 part 2

src/day05/mod.rs

@@ -4,54 +4,61 @@ pub fn run() {
     let input = read("05");
 
     let lines = input.split_once("\n\n").unwrap();
-    let stackslines = lines.0.lines().collect::<Vec<_>>();
-    let mut stacks = std::collections::HashMap::new();
-    for l in stackslines {
+    let mut stacks: Vec<Vec<char>> = lines
+    .0
+    .lines()
+    .fold(vec![], |mut agg, l| {
         let length = l.len();
         let mut idx = 0;
         while idx <= length {
-            let charnum = 1 + idx * 4;
-            if let Some(s1) = l.chars().nth(charnum) {
+            if let Some(s1) = l.chars().nth(1 + idx * 4) {
                 if !s1.is_whitespace() && !s1.is_numeric() {
-                    let e = stacks.entry(idx + 1).or_insert(vec![]);
-                    e.push(s1);
+                    while idx >= agg.len() {
+                        agg.push(vec![]);
+                    }
+                    agg.get_mut(idx).unwrap().push(s1);
                 }
             }
             idx += 1;
         }
-    }
-    let k = stacks.keys().max().unwrap();
-    for i in 1..=*k {
-        stacks.entry(i).and_modify(|s| s.reverse());
-    }
+        agg
+    });
+    stacks.iter_mut().for_each(|s|s.reverse());
 
     let re = regex::Regex::new(r"move (\d+) from (\d+) to (\d+)").unwrap();
-    for l in lines.1.lines().filter(|l| !l.is_empty()) {
-        let capt = re.captures(l).unwrap();
-        let count: usize = capt[1].parse().unwrap();
-        let from: usize = capt[2].parse().unwrap();
-        let to: usize = capt[3].parse().unwrap();
-        for _i in 0..count {
-            let fr = stacks.get_mut(&from).unwrap();
-            let c = fr.pop().unwrap();
-            stacks.entry(to).and_modify(|s| s.push(c));
-        }
-    }
+    let instructions = lines.1.lines()
+        .filter(|l| !l.is_empty())
+        .map(|l| {
+            let capt = re.captures(l).unwrap();
+            (capt[1].parse::<usize>().unwrap(),
+             capt[2].parse::<usize>().unwrap() - 1,
+             capt[3].parse::<usize>().unwrap() - 1)
+        }).collect::<Vec<_>>();
 
     #[cfg(feature = "part1")]
     {
-        let mut keys = stacks.keys().copied().collect::<Vec<_>>();
-        keys.sort();
-        let chars = keys
-            .iter()
-            .map(|s| stacks.get(s).unwrap().last().unwrap())
+        let mut stacks = stacks.clone();
+        instructions.iter().for_each(|(count, from, to)| {
+            for _i in 0..*count {
+                let c2 = stacks.get_mut(*from).unwrap().pop().unwrap();
+                stacks.get_mut(*to).unwrap().push(c2);
+            }
+        });
+        let chars = stacks.iter().map(|s|s.last().unwrap())
             .collect::<String>();
         println!("Day 5, Part 01: {}", chars);
     }
 
     #[cfg(feature = "part2")]
     {
-        let count = 1;
-        println!("Day 5, Part 02: {}", count);
+        instructions.iter().for_each(|(count, from, to)| {
+            let src = stacks.get_mut(*from).unwrap();
+            let range = src.len()-count..;
+            let mut crates = src.drain(range).collect();
+            stacks.get_mut(*to).unwrap().append(&mut crates);
+        });
+        let chars = stacks.iter().map(|s|s.last().unwrap())
+            .collect::<String>();
+        println!("Day 5, Part 02: {}", chars);
     }
 }