neon

y2021/p24.py

+def valid_z1s(z2, w, c1, c2, c3):
+    valid = {(z2 - w - c3) // 26} | {(z2 * 26 + i) for i in range(26)}
+    for z1 in valid:
+        if z1 < 26 ** exp:
+            if evolve(z1, w, c1, c2, c3) == z2:
+                yield z1
+
+
+def evolve(z, w, c1, c2, c3):
+    return (z // c1) if (z % 26 + c2 == w) else (z * 26 + w + c3)
+
+
+consts = [
+    (int(els[4]), int(els[5]), int(els[15]))
+    for block in open(0).read().split('inp w')[1:]
+    for els in [[ln.split()[-1] for ln in block.splitlines()]]
+]
+state = [('', 0)]
+for exp, (c1, c2, c3) in list(enumerate(consts, 1))[::-1]:
+    print(exp, len(state))
+    state = [
+        (w + s, z1)
+        for s, z2 in state
+        for w in '123456789'
+        for z1 in valid_z1s(z2, int(w), c1, c2, c3)
+    ]
+
+(head, _), *body, (tail, _) = sorted(state)
+print(tail)
+print(head)