k

1 files changed, 49 insertions, 0 deletions

diff --git a/2024/22/solve.py b/2024/22/solve.py
new file mode 100755
index 0000000..f6fe00f
--- /dev/null
+++ b/2024/22/solve.py
@@ -0,0 +1,49 @@
+#!/bin/env python3
+
+L = [int(l.strip()) for l in open("input").readlines()]
+
+
+def evolve(n):
+    n ^= n * 64
+    n %= 16777216
+
+    n ^= n // 32
+    n %= 16777216
+
+    n ^= n * 2048
+    n %= 16777216
+
+    return n
+
+
+def part1(n):
+    for i in range(2000):
+        n = evolve(n)
+    return n
+
+
+def part2():
+    M = {}
+    for n in L:
+        diffs = []
+        vals = [0]
+        for i in range(2000):
+            n = evolve(n)
+            s = n % 10
+            diffs.append(s - vals[-1])
+            vals.append(s)
+
+        s = set()
+        for i in range(4, len(vals)):
+            r = tuple(diffs[i - 4 : i])
+            if r not in s:
+                if r in M:
+                    M[r] += vals[i]
+                else:
+                    M[r] = vals[i]
+                s.add(r)
+    return M[max(M, key=M.get)]
+
+
+print(sum(part1(n) for n in L))
+print(part2())