day 5 part 2 was meh

src/bin/05.rs

@@ -56,9 +56,21 @@ pub fn part_one(input: &str) -> Option<String> {
 }
 
 pub fn part_two(input: &str) -> Option<String> {
-    let _ = input;
+    let parts: Vec<&str> = input.split("\n\n").collect();
+    let mut stacks = parse_stacks(parts[0]);
+    let instructions = parse_instructions(parts[1]);
+    for i in instructions {
+        let mut new = Vec::new();
 
-    None
+        for _ in 0..(i.amount) {
+            let x = stacks[i.from-1].pop().unwrap();
+            new.insert(0,x);
+        }
+        stacks[i.to-1].append(&mut new);
+    }
+    Some(stacks.iter()
+    .map(| x | x[x.len()-1].to_string()) // stringify top element of every stack
+    .reduce(| x, y | x + &y).unwrap()) // and merge into one big string
 }
 
 fn main() {
@@ -80,6 +92,6 @@ mod tests {
     #[test]
     fn test_part_two() {
         let input = advent_of_code::read_file("examples", 5);
-        assert_eq!(part_two(&input), None);
+        assert_eq!(part_two(&input), Some("MCD".to_string()));
     }
 }