Day 7, Parts 1 + 2

Doing this one in Rust kicked my ass. I fought with the compiler for three
days and never was able to figure out the borrows and pointers.

I gave up yesterday and wrote up a solution in Python. Maybe I'll come back to
it one day.

2022/day7.py

@@ -0,0 +1,125 @@
+#!/usr/bin/env python3
+# Eryn Wells <eryn@erynwells.me>
+
+'''
+New script.
+'''
+
+import argparse
+
+TOTAL_DISK_SIZE = 70000000
+SIZE_REQUIRED_FOR_UPDATE = 30000000
+
+class File:
+    def __init__(self, name, size):
+        self.name = name
+        self.size = size
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.name!r}, {self.size!r})'
+
+class Directory:
+    def __init__(self, name):
+        self.name = name
+        self.directories = {}
+        self.files = []
+        self.parent = None
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.name!r})'
+
+    def add_subdirectory(self, subdirectory):
+        assert subdirectory.name not in self.directories
+        self.directories[subdirectory.name] = subdirectory
+        subdirectory.parent = self
+
+    def add_file(self, file):
+        self.files.append(file)
+
+    @property
+    def size(self):
+        size_of_directories = sum(d.size for d in self.directories.values())
+        size_of_files = sum(f.size for f in self.files)
+        return size_of_directories + size_of_files
+
+    def pretty_print(self, indent=0):
+        print(' ' * indent, self.name, f'({self.size})')
+        for d in self.directories.values():
+            d.pretty_print(indent=indent+2)
+        for f in self.files:
+            print(' ' * (indent + 2), repr(f))
+
+def parse_args(argv, *a, **kw):
+    parser = argparse.ArgumentParser(*a, **kw)
+    parser.add_argument('input')
+    args = parser.parse_args(argv)
+    return args
+
+def main(argv):
+    args = parse_args(argv[1:], prog=argv[0])
+
+    with open(args.input) as f:
+        lines = f.readlines()
+
+    print(f'{len(lines)} total lines in input file {args.input}')
+
+    root = Directory('/')
+    cwd = root
+
+    for line in lines:
+        split_line = line.strip().split(' ')
+        if split_line[0] == '$':
+            if split_line[1] == 'cd':
+                dir_name = split_line[2].strip()
+                if dir_name == '/':
+                    cwd = root
+                elif dir_name == '..':
+                    cwd = cwd.parent
+                else:
+                    cwd = cwd.directories[dir_name]
+                print(f'Set cwd to {cwd}')
+            elif split_line[1] == 'ls':
+                print(f'Nothing to do for `ls` in {cwd}')
+                # Nothing to do here.
+                pass
+        elif split_line[0] == 'dir':
+            # dir [name]
+            name = split_line[1]
+            print(f'Found subdirectory {name} in {cwd}')
+            cwd.add_subdirectory(Directory(name))
+        else:
+            # [size] [name]
+            name = split_line[1]
+            size = int(split_line[0])
+            print(f'Found file {name} with size {size} in {cwd}')
+            cwd.add_file(File(name, size))
+
+    root.pretty_print()
+    print(f'Part 0: total size of the entire tree: {root.size}')
+
+    root_size = root.size
+    free_space = TOTAL_DISK_SIZE - root_size
+    minimum_size_of_directory_to_delete = SIZE_REQUIRED_FOR_UPDATE - free_space
+
+    part1_sum = 0
+    part2_directories = []
+    dfs_stack = [root]
+    while len(dfs_stack):
+        d = dfs_stack.pop()
+        dfs_stack.extend(d.directories.values())
+        dir_size = d.size
+        if dir_size <= 100000:
+            part1_sum += dir_size
+        if dir_size > minimum_size_of_directory_to_delete:
+            part2_directories.append(d)
+
+    print(f'Part 1: total size of directories with size less than 100,000: {part1_sum}')
+
+    directory_to_delete = min(part2_directories, key=lambda d: d.size)
+    print(f'Part 2: size of directory to delete: {directory_to_delete.size}')
+
+
+if __name__ == '__main__':
+    import sys
+    result = main(sys.argv)
+    sys.exit(0 if not result else result)