2022: d05: ex2: add solution

2022/d05/ex2/ex2.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+
+import dataclasses
+import sys
+
+Stack = list[str]
+
+
+@dataclasses.dataclass
+class Instruction:
+    n: int
+    start: int
+    end: int
+
+    @classmethod
+    def from_input(cls, input: str) -> "Instruction":
+        words = input.split()
+        return Instruction(int(words[1]), int(words[3]) - 1, int(words[5]) - 1)
+
+
+def parse(input: list[str]) -> tuple[list[Stack], list[Instruction]]:
+    def parse_stacks(input: list[str]) -> list[Stack]:
+        stacks: list[Stack] = [[] for _ in range(1, len(input[-1]), 4)]
+        for line in reversed(input[:-1]):
+            for stack, i in enumerate(range(1, len(line), 4)):
+                c = line[i]
+                if c == " ":
+                    continue
+                stacks[stack].append(c)
+        return stacks
+
+    def parse_instructions(input: list[str]) -> list[Instruction]:
+        return list(map(Instruction.from_input, input))
+
+    empty_line = input.index("")
+
+    return parse_stacks(input[:empty_line]), parse_instructions(input[empty_line + 1 :])
+
+
+def solve(input: list[str]) -> str:
+    stacks, instructions = parse(input)
+    for instr in instructions:
+        start, end = stacks[instr.start], stacks[instr.end]
+        items = [start.pop() for _ in range(instr.n)]
+        items.reverse()
+        end.extend(items)
+    return "".join(stack[-1] for stack in stacks if stack)
+
+
+def main() -> None:
+    input = sys.stdin.read().splitlines()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()