my brain hurts

7/nospaceleft.py

@@ -3,14 +3,25 @@ from collections import defaultdict
 from aocd.models import Puzzle
 from aocd import submit
 
-
-def get_sizes(dirs: dict, max_size: int) -> int:
+def get_sizes_a(dirs: dict, max_size: int) -> int:
     """
-    gather all filesizes from the input
+    return the size of all dirs which are at most max_size big
     """
     filtered_dirs = [ value for value in dirs.values() if value < max_size]
     return sum(filtered_dirs)
 
+def get_sizes_b(dirs: dict, needed_size: int) -> int:
+    """
+    return the smallest size of a dir which when deleted amounts
+    to the needed size of 30M.
+    """
+    total_size = 70000000
+    used_size = dirs[('/',)]
+    max_free = needed_size - (total_size - used_size)
+    filtered_dirs = [ value for value in dirs.values() if value > max_free]
+    return min(filtered_dirs)
+
+
 def parse_input(input_str: str) -> list:
     """
     the input string consists of the following four message types
@@ -48,11 +59,11 @@ if __name__ == "__main__":
     dirs = parse_input(puzzle.input_data)
 
     # part a: get the sum of all dirs where the size is at most 100k
-    answer_a = get_sizes(dirs, 100000)
+    answer_a = get_sizes_a(dirs, 100000)
     print(f"{answer_a}")
     submit(answer_a, part="a", day=7, year=2022)
 
-    # part b:
-    answer_b = get_sizes(dirs, 100)
+    # part b: find the smallest D (huehue) that will free up at least 30M
+    answer_b = get_sizes_b(dirs, 30000000)
     print(f"{answer_b}")
-    #submit(answer_b, part="b", day=7, year=2022)
+    submit(answer_b, part="b", day=7, year=2022)