Poetry stuff.

src/holt59/aoc/2021/day8.py

@@ -0,0 +1,87 @@
+import itertools
+import os
+import sys
+
+VERBOSE = os.getenv("AOC_VERBOSE") == "True"
+
+digits = {
+    "abcefg": 0,
+    "cf": 1,
+    "acdeg": 2,
+    "acdfg": 3,
+    "bcdf": 4,
+    "abdfg": 5,
+    "abdefg": 6,
+    "acf": 7,
+    "abcdefg": 8,
+    "abcdfg": 9,
+}
+
+lines = sys.stdin.read().splitlines()
+
+# part 1
+lengths = {len(k) for k, v in digits.items() if v in (1, 4, 7, 8)}
+answer_1 = sum(
+    len(p) in lengths for line in lines for p in line.split("|")[1].strip().split()
+)
+print(f"answer 1 is {answer_1}")
+
+# part 2
+values: list[int] = []
+
+for line in lines:
+    parts = line.split("|")
+    broken_digits = sorted(parts[0].strip().split(), key=len)
+
+    per_length = {
+        k: list(v)
+        for k, v in itertools.groupby(sorted(broken_digits, key=len), key=len)
+    }
+
+    # a can be found immediately
+    a = next(u for u in per_length[3][0] if u not in per_length[2][0])
+
+    # c and f have only two possible values corresponding to the single entry of
+    # length 2
+    cf = list(per_length[2][0])
+
+    # the only digit of length 4 contains bcdf, so we can deduce bd by removing cf
+    bd = [u for u in per_length[4][0] if u not in cf]
+
+    # the 3 digits of length 5 have a, d and g in common
+    adg = [u for u in per_length[5][0] if all(u in pe for pe in per_length[5][1:])]
+
+    # we can remove a
+    dg = [u for u in adg if u != a]
+
+    # we can deduce d and g
+    d = next(u for u in dg if u in bd)
+    g = next(u for u in dg if u != d)
+
+    # then b
+    b = next(u for u in bd if u != d)
+
+    # f is in the three 6-length digits, while c is only in 2
+    f = next(u for u in cf if all(u in p for p in per_length[6]))
+
+    # c is not f
+    c = next(u for u in cf if u != f)
+
+    # e is the last one
+    e = next(u for u in "abcdefg" if u not in {a, b, c, d, f, g})
+
+    mapping = dict(zip((a, b, c, d, e, f, g), "abcdefg"))
+
+    value = 0
+    for number in parts[1].strip().split():
+        digit = "".join(sorted(mapping[c] for c in number))
+        value = 10 * value + digits[digit]
+
+    if VERBOSE:
+        print(value)
+
+    values.append(value)
+
+
+answer_2 = sum(values)
+print(f"answer 2 is {answer_2}")