1 files changed, 68 insertions, 0 deletions
diff --git a/2024/17/python.py b/2024/17/python.py
new file mode 100755
index 0000000..9ea7de4
--- /dev/null
+++ b/2024/17/python.py
@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+
+from fileinput import input
+from itertools import takewhile, zip_longest
+
+inp = map(str.strip, input())
+regs = [int(r[2]) for r in (line.split() for line in takewhile(bool, inp))]
+prog = [int(o) for o in next(inp).split()[1].split(",")]
+out = []
+
+
+def run(prog, ra, rb, rc):
+    out = []
+    ir = 0
+    while ir < len(prog):
+        instr, op = prog[ir], prog[ir + 1]
+        combo = {4: ra, 5: rb, 6: rc}
+        cop = combo.get(op, op)
+        match instr:
+            case 0:
+                ra = ra >> cop
+            case 1:
+                rb ^= op
+            case 2:
+                rb = cop & 0b111
+            case 3 if ra:
+                ir = op - 2
+            case 4:
+                rb ^= rc
+            case 5:
+                yield cop & 0b111
+            case 6:
+                rb = ra >> cop
+            case 7:
+                rc = ra >> cop
+        ir += 2
+    return out
+
+
+def match(prog, ra):
+    return (
+        got == want
+        for got, want in zip_longest(
+            reversed(list(run(prog, ra, 0, 0))),
+            reversed(prog),
+        )
+    )
+
+
+def find_a(prog):
+    q = list(range(8))
+    while True:
+        curr = q.pop(0)
+        if all(match(prog, curr)):
+            return curr
+
+        best = sum(match(prog, curr))
+        for n in range(8):
+            ra = (curr << 3) + n
+            if sum(match(prog, ra)) > best:
+                q.append(ra)
+
+
+silver = ",".join(map(str, run(prog, *regs)))
+gold = find_a(prog)
+
+print("silver:", silver)
+print("gold:", gold)