day5 part 2

day5/README.md

@@ -74,6 +74,72 @@ Finally, one crate is moved from stack 1 to stack 2:
 ```
 
 The Elves just need to know **which crate will end up on top of each stack**; in this example, the top crates are `C` in
-stack 1, `M` in stack 2, and `Z` in stack 3, so you should combine these together and give the Elves the message `CMZ`.
+stack 1, `M` in stack 2, and `Z` in stack 3, so you should combine these together and give the Elves the message **CMZ
+**.
 
 **After the rearrangement procedure completes, what crate ends up on top of each stack?**
+
+# Part Two
+
+As you watch the crane operator expertly rearrange the crates, you notice the process isn't following your prediction.
+
+Some mud was covering the writing on the side of the crane, and you quickly wipe it away. The crane isn't a CrateMover
+9000 - it's a **CrateMover 9001**.
+
+The CrateMover 9001 is notable for many new and exciting features: air conditioning, leather seats, an extra cup holder,
+and the **ability to pick up and move multiple crates at once**.
+
+Again considering the example above, the crates begin in the same configuration:
+
+```
+    [D]    
+[N] [C]    
+[Z] [M] [P]
+ 1   2   3 
+```
+
+Moving a single crate from stack 2 to stack 1 behaves the same as before:
+
+```
+[D]        
+[N] [C]    
+[Z] [M] [P]
+ 1   2   3 
+```
+
+However, the action of moving three crates from stack 1 to stack 3 means that those three moved crates **stay in the
+same order**, resulting in this new configuration:
+
+```
+        [D]
+        [N]
+    [C] [Z]
+    [M] [P]
+ 1   2   3 
+```
+
+Next, as both crates are moved from stack 2 to stack 1, they **retain their order as well**:
+
+```
+        [D]
+        [N]
+[C]     [Z]
+[M]     [P]
+ 1   2   3 
+```
+
+Finally, a single crate is still moved from stack 1 to stack 2, but now it's crate C that gets moved:
+
+```
+        [D]
+        [N]
+        [Z]
+[M] [C] [P]
+ 1   2   3 
+```
+
+In this example, the CrateMover 9001 has put the crates in a totally different order: **MCD**.
+
+Before the rearrangement process finishes, update your simulation so that the Elves know where they should stand to be
+ready to unload the final supplies. **After the rearrangement procedure completes, what crate ends up on top of each
+stack?**

day5/main.py

@@ -22,6 +22,38 @@ class Move:
     to: int
 
 
+def top_crates_1(data: list) -> str:
+    stacks, instructions = process_data(data)
+    stacks = find_top_crates_1(stacks, instructions)
+    return output_top_crates(stacks)
+
+
+def find_top_crates_1(stacks: list[list[str]], instructions: list[Move]) -> list[list[str]]:
+    for step in instructions:
+        for _ in range(step.quantity):
+            stacks[step.to].append(stacks[step.of].pop())
+
+    return stacks
+
+
+def find_top_crates_2(stacks: list[list[str]], instructions: list[Move]) -> list[list[str]]:
+    for step in instructions:
+        tmp = []
+        print(tmp)
+        for _ in range(step.quantity):
+            tmp.insert(0, stacks[step.of].pop())
+            print(tmp)
+        stacks[step.to].extend(tmp)
+
+    return stacks
+
+
+def top_crates_2(data: list[str]) -> str:
+    stacks, instructions = process_data(data)
+    stacks = find_top_crates_2(stacks, instructions)
+    return output_top_crates(stacks)
+
+
 def process_data(data: list[str]) -> tuple[list[list[str]], list[Move]]:
     rows = []
     steps = []
@@ -66,21 +98,15 @@ def _build_instructions(instructions: list[str]) -> list[Move]:
     return moves
 
 
-def find_top_crates(stacks: list[list[str]], instructions: list[Move]) -> str:
-    for step in instructions:
-        for _ in range(step.quantity):
-            stacks[step.to].append(stacks[step.of].pop())
-
+def output_top_crates(stacks) -> str:
     return "".join(stack[-1] for stack in stacks)
 
 
-def top_crates(data: list) -> str:
-    stacks, instructions = process_data(data)
-    return find_top_crates(stacks, instructions)
-
-
 if __name__ == "__main__":
     dataset = read_data()
 
-    res = top_crates(dataset)
+    res = top_crates_1(dataset)
     assert res == "CMZ", f"{res} is not the right value"
+
+    res = top_crates_2(dataset)
+    assert res == "MCD", f"{res} is not the right value"