2022: d07: ex2: add solution

2022/d07/ex2/ex2.py

@@ -0,0 +1,70 @@
+#!/usr/bin/env python
+
+import sys
+from typing import Union
+
+FileSystem = dict[str, Union[int, "FileSystem"]]
+
+
+def solve(input: list[str]) -> int:
+    def build_tree(input: list[str], i: int = 0) -> tuple[FileSystem, int]:
+
+        fs: FileSystem = {}
+
+        while i < len(input):
+            assert input[i][0] == "$"  # Sanity check
+            command = input[i].split()[1:]
+            if command[0] == "ls":
+                while (i := i + 1) < len(input):
+                    if input[i][0] == "$":
+                        break
+                    else:
+                        type, name = input[i].split()
+                        if type == "dir":
+                            continue
+                        fs[name] = int(type)
+            elif command[0] == "cd":
+                if command[1] == "..":
+                    i += 1
+                    break
+                else:
+                    fs[command[1]], i = build_tree(input, i + 1)
+            else:
+                assert False  # Sanity check
+
+        return fs, i
+
+    def total_size(
+        fs: FileSystem, parent_path: str = ""
+    ) -> dict[str, tuple[int, bool]]:
+        sizes: dict[str, tuple[int, bool]] = {}
+
+        for f, content in fs.items():
+            path = f"{parent_path}/{f}"
+            if isinstance(content, int):
+                sizes[path] = content, False
+            elif isinstance(content, dict):
+                children_sizes = total_size(content, path)
+                total = sum(children_sizes[f"{path}/{c}"][0] for c in content.keys())
+                sizes[path] = total, True
+                sizes.update(children_sizes)
+            else:
+                assert False  # Sanity check
+
+        return sizes
+
+    fs, i = build_tree(input)
+    assert i == len(input)  # Sanity check
+    sizes = total_size(fs)
+    THRESHOLD = 30000000 - (70000000 - sizes["//"][0])
+    assert THRESHOLD > 0  # Sanity check
+    return min(size for size, is_dir in sizes.values() if is_dir and size >= THRESHOLD)
+
+
+def main() -> None:
+    input = sys.stdin.read().splitlines()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()