Day 25

25.py

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+#!/usr/bin/python3
+
+"""Solution for day 25 of Advent of Code 2016.
+
+This is a copy of Day 23's solution, with an 'out' instruction added.
+
+Manual testing showed the output repeats regularly, so we just run the program until there are 20 bits output.
+"""
+import itertools
+
+
+def value(registers, x):
+    try:
+        return int(x)
+    except ValueError:
+        return registers[x]
+
+
+def cpy(registers, src, dst):
+    registers[dst] = value(registers, src)
+
+
+def inc(registers, reg):
+    registers[reg] += 1
+
+
+def dec(registers, reg):
+    registers[reg] -= 1
+
+
+def jnz(registers, val, tar):
+    registers['pc'] += 0 if value(registers, val) == 0 else value(registers, tar) - 1
+
+
+def tgl(registers, ins):
+    mappings = {inc: dec, dec: inc, tgl: inc, jnz: cpy, cpy: jnz}
+    target = registers['pc'] + value(registers, ins)
+    registers['in'][target] = (mappings[registers['in'][target][0]], registers['in'][target][1])
+
+
+def out(registers, val):
+    registers['out'].append(value(registers, val))
+
+
+def try_multiply(registers):
+    try:
+        pc = registers['pc']
+        chunk = registers['in'][pc:pc+6]
+        instr, args = map(list, zip(*chunk))
+        if instr == [cpy, inc, dec, jnz, dec, jnz] \
+                and args[0][1] == args[2][0] == args[3][0] \
+                and args[4][0] == args[5][0] \
+                and args[1][0] != args[0][1] != args[4][0] != args[0][0] \
+                and args[3][1] == '-2' and args[5][1] == '-5':
+            registers[args[1][0]] += value(registers, args[0][0]) * value(registers, args[4][0])
+            registers[args[2][0]] = 0
+            registers[args[4][0]] = 0
+            registers['pc'] += 5
+            return True
+    except:
+        pass
+    return False
+
+
+def step(registers):
+    if not try_multiply(registers):
+        try:
+            registers['in'][registers['pc']][0](registers, *registers['in'][registers['pc']][1])
+        except:
+            pass
+
+
+def run(values):
+    registers = values
+    registers['pc'] = 0
+    registers['out'] = []
+    registers['in'] = instr.copy()
+
+    while registers['pc'] < len(instr) and len(registers['out']) < 20:
+        step(registers)
+        registers['pc'] += 1
+
+    return registers['out']
+
+
+with open('data/25.txt', 'r') as file:
+    instr = map(str.split, map(str.strip, file.readlines()))
+    instr = [(globals()[i[0]], i[1:]) for i in instr]
+
+for a in itertools.count():
+    if run({'a': a, 'b': 0, 'c': 0, 'd': 0}) == [0, 1] * 10:
+        print('Part one: %s' % a)
+        break

data/25.txt

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+cpy a d
+cpy 7 c
+cpy 365 b
+inc d
+dec b
+jnz b -2
+dec c
+jnz c -5
+cpy d a
+jnz 0 0
+cpy a b
+cpy 0 a
+cpy 2 c
+jnz b 2
+jnz 1 6
+dec b
+dec c
+jnz c -4
+inc a
+jnz 1 -7
+cpy 2 b
+jnz c 2
+jnz 1 4
+dec b
+dec c
+jnz 1 -4
+jnz 0 0
+out b
+jnz a -19
+jnz 1 -21