2024 day 22.

src/holt59/aoc/2024/day22.py

@@ -3,5 +3,57 @@ from typing import Any, Iterator
 from ..base import BaseSolver
 
 
+def mix(secret: int, value: int) -> int:
+    return secret ^ value
+
+
+def prune(secret: int) -> int:
+    return secret % 16777216
+
+
+def next_number(secret: int) -> int:
+    # Calculate the result of multiplying the secret number by 64. Then, mix this
+    # result into the secret number. Finally, prune the secret number.
+    secret = prune(mix(secret, secret * 64))
+
+    # Calculate the result of dividing the secret number by 32. Round the result down
+    # to the nearest integer. Then, mix this result into the secret number. Finally,
+    # prune the secret number.
+    secret = prune(mix(secret, secret // 32))
+
+    # Calculate the result of multiplying the secret number by 2048. Then, mix this
+    # result into the secret number. Finally, prune the secret number.
+    secret = prune(mix(secret, secret * 2048))
+
+    return secret
+
+
 class Solver(BaseSolver):
-    def solve(self, input: str) -> Iterator[Any]: ...
+    def solve(self, input: str) -> Iterator[Any]:
+        starts = [int(r) for r in input.splitlines()]
+
+        ends: list[int] = []
+        prices: list[int] = [0 for _ in range(2**16)]
+
+        for secret in self.progress.wrap(starts):
+            checked: list[bool] = [False] * len(prices)
+            hashed: int = 0
+
+            for i in range(2000):
+                last = secret % 10
+                secret = next_number(secret)
+                next = secret % 10
+
+                hashed = ((hashed << 4) & 0xFFFF) | ((last - next) & 0xF)
+
+                if i >= 3 and not checked[hashed]:
+                    checked[hashed] = True
+                    prices[hashed] += next
+
+            ends.append(secret)
+
+        for start, end in zip(starts, ends, strict=True):
+            self.logger.info(f"{start}: {end}")
+
+        yield sum(ends)
+        yield max(prices)

src/holt59/aoc/inputs/tests/2024/day22.txt

@@ -0,0 +1,4 @@
+1
+10
+100
+2024

src/holt59/aoc/inputs/tests/2024/day22_p2.txt

@@ -0,0 +1,4 @@
+1
+2
+3
+2024