Solve day 17

2024/17_computer.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+import sys
+import re
+
+def run(program, regs):
+    a, b, c = range(4, 7)
+    ip = 0
+    combo = [0, 1, 2, 3, *regs]
+    while ip < len(program):
+        opcode, operand = program[ip:ip + 2]
+        if opcode == 0:
+            combo[a] >>= combo[operand]
+        elif opcode == 1:
+            combo[b] ^= operand
+        elif opcode == 2:
+            combo[b] = combo[operand] % 8
+        elif opcode == 3:
+            if combo[a]:
+                ip = operand - 2
+        elif opcode == 4:
+            combo[b] ^= combo[c]
+        elif opcode == 5:
+            yield combo[operand] % 8
+        elif opcode == 6:
+            combo[b] = combo[a] >> combo[operand]
+        elif opcode == 7:
+            combo[c] = combo[a] >> combo[operand]
+        ip += 2
+
+def expect(program, out, prev_a=0):
+    if not out:
+        return prev_a
+    for a in range(1 << 10):
+        if a >> 3 == prev_a & 127 and next(run(program, (a, 0, 0))) == out[-1]:
+            ret = expect(program, out[:-1], (prev_a << 3) | (a % 8))
+            if ret is not None:
+                return ret
+
+nums = list(map(int, re.findall(r'\d+', sys.stdin.read())))
+regs = nums[:3]
+program = nums[3:]
+print(','.join(map(str, run(program, regs))))
+print(expect(program, program))

2024/input/17

@@ -0,0 +1,5 @@
+Register A: 30118712
+Register B: 0
+Register C: 0
+
+Program: 2,4,1,3,7,5,4,2,0,3,1,5,5,5,3,0