Continue with 2016 and 2017.

2016/d14.py

@@ -0,0 +1,57 @@
+import hashlib
+from dataclasses import dataclass
+
+
+@dataclass
+class Candidate:
+    char: str
+    age: int
+    orig_hash: int
+    conf_hash: int = 0
+
+data = "cuanljph"
+# data = "abc"
+
+keys = []
+candidates = []
+rehashs = 2016 # part 2
+rehashs = 0 # part 1
+
+for hash_idx in range(0, 100_000):
+    h = hashlib.md5(f"{data}{hash_idx}".encode()).hexdigest()
+    for _ in range(rehashs):
+        h = hashlib.md5(h.encode()).hexdigest()
+
+    idx3 = None
+    for i in range(len(h) - 3):
+        if all([h[i] == h[i + j] for j in range(3)]):
+            idx3 = i
+            break
+
+    if idx3 is not None:
+        candidates.append(Candidate(h[idx3], 0, hash_idx))
+
+    letters = []
+    for i in range(len(h) - 5):
+        if all([h[i] == h[i + j] for j in range(5)]):
+            letters.append(h[i])
+
+    for current_char in set(letters):
+        for c in candidates:
+            if c.char == current_char and c.age > 0:
+                # print(f"Confirmed {c} at {hash_idx}.")
+                keys.append(c)
+                c.age = 1000 # mark for removal from candidates
+                c.conf_hash = hash_idx
+
+    if len(keys) >= 64:
+        # print("done")
+        break
+
+    # remove old candidates
+    candidates = [c for c in candidates if c.age < 1000]
+    for c in candidates:
+        c.age += 1
+
+keys.sort(key=lambda c: c.orig_hash)
+print(keys[63].orig_hash)

2016/d15.py

@@ -0,0 +1,45 @@
+import sys
+from lib import str_to_ints
+from copy import deepcopy
+
+with open("i15.txt") as f:
+    d = f.read()
+
+part_2 = True
+if part_2:
+    d += "#7 11 0  0"
+
+discs = []
+for line in d.splitlines():
+    id, npos, time, cpos = str_to_ints(line)
+    discs.append([cpos, npos])
+
+qpos = -1
+orig_discs = deepcopy(discs)
+
+# empirically could dev algo to find or CRT?
+if part_2:
+    start, delta = 12136, 33915
+else:
+    start, delta = 831, 2261
+
+for start_time in range(start, 1_000_000_000, delta):
+    discs = deepcopy(orig_discs)
+
+    # let discs move for initial wait
+    for _ in range(start_time):
+        for disc in discs:
+            disc[0] = (disc[0] + 1) % disc[1]
+
+    # drop the capsule 
+    for i in range(len(discs)):
+        # discs move first
+        for disc in discs:
+            disc[0] = (disc[0] + 1) % disc[1]
+
+        # check if there is a collission for the current disc
+        if discs[i][0] != 0:
+            break
+    else:
+        print(start_time)
+        sys.exit(0)