day 7

Author: schoblaska

07/a.rb

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+fs = { "/" => {} }
+pwd = []
+
+File.foreach("07/input.txt", chomp: true) do |line|
+  if chdir = line[/\$ cd (.+)/, 1]
+    chdir == ".." ? pwd.pop : pwd << chdir
+  elsif dirname = line[/dir (.+)/, 1]
+    fs.dig(*pwd)[dirname] = {}
+  elsif filematch = line.match(/(\d+) (.+)/)
+    fs.dig(*pwd)[filematch[2]] = filematch[1].to_i
+  end
+end
+
+def dir_sizes(fs, pwd = ["/"])
+  dir = fs.dig(*pwd)
+  subdirs = dir.keys.select { |k| dir[k].is_a?(Hash) }
+  subdir_sizes = subdirs.map { |d| dir_sizes(fs, pwd + [d]) }.reduce(:merge)
+  local_size = dir.values.sum { |i| i.is_a?(Integer) ? i : 0 }
+  total_size = local_size + subdirs.sum { |d| subdir_sizes[pwd + [d]] }
+
+  { pwd => total_size }.merge(subdir_sizes || {})
+end
+
+p dir_sizes(fs).values.sum { |s| s <= 100_000 ? s : 0 }

07/b.rb

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+fs = { "/" => {} }
+pwd = []
+
+File.foreach("07/input.txt", chomp: true) do |line|
+  if chdir = line[/\$ cd (.+)/, 1]
+    chdir == ".." ? pwd.pop : pwd << chdir
+  elsif dirname = line[/dir (.+)/, 1]
+    fs.dig(*pwd)[dirname] = {}
+  elsif filematch = line.match(/(\d+) (.+)/)
+    fs.dig(*pwd)[filematch[2]] = filematch[1].to_i
+  end
+end
+
+def dir_sizes(fs, pwd = ["/"])
+  dir = fs.dig(*pwd)
+  subdirs = dir.keys.select { |k| dir[k].is_a?(Hash) }
+  subdir_sizes = subdirs.map { |d| dir_sizes(fs, pwd + [d]) }.reduce(:merge)
+  local_size = dir.values.sum { |i| i.is_a?(Integer) ? i : 0 }
+  total_size = local_size + subdirs.sum { |d| subdir_sizes[pwd + [d]] }
+
+  { pwd => total_size }.merge(subdir_sizes || {})
+end
+
+disk = 70_000_000
+needed = 30_000_000
+ps = dir_sizes(fs)
+avail = disk - ps[["/"]]
+
+p ps.values.sort.find { |v| v >= needed - avail }

07/example.txt

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+$ cd /
+$ ls
+dir a
+14848514 b.txt
+8504156 c.dat
+dir d
+$ cd a
+$ ls
+dir e
+29116 f
+2557 g
+62596 h.lst
+$ cd e
+$ ls
+584 i
+$ cd ..
+$ cd ..
+$ cd d
+$ ls
+4060174 j
+8033020 d.log
+5626152 d.ext
+7214296 k