185 lines
4.6 KiB
Python
185 lines
4.6 KiB
Python
#!/usr/bin/env python3
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import re
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from random import randrange
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from array import array
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from copy import copy
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class VM():
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def __init__(self, reg: array = array('q'), mem: list = [], pc: int = 0):
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self.reg = copy(reg)
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self.mem = copy(mem)
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self.pc = copy(pc)
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self.outbuf = []
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def _combo(self, c) -> int:
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if c == 0: return 0
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if c == 1: return 1
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if c == 2: return 2
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if c == 3: return 3
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if c == 4: return self.reg[0]
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if c == 5: return self.reg[1]
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if c == 6: return self.reg[2]
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raise RuntimeError()
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def run(self, abort: int = 0):
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while self.pc < len(self.mem):
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if abort>0 and len(self.mem) > abort: return
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op = self.mem[self.pc]
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self.pc += 1
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if op == 0b000: # adv
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self.reg[0] = self.reg[0] // (2**self._combo(self.mem[self.pc]))
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self.pc += 1
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if op == 0b001: # bxl
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self.reg[1] = self.reg[1] ^ self.mem[self.pc]
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self.pc += 1
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if op == 0b010: # bst
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self.reg[1] = self._combo(self.mem[self.pc]) & 0b111
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self.pc += 1
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if op == 0b011: # jnz
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self.pc = self.mem[self.pc] if self.reg[0] != 0 else self.pc+1
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if op == 0b100: # bxc
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self.reg[1] = self.reg[1] ^ self.reg[2]
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self.pc += 1
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if op == 0b101: # out
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self.outbuf.append(self._combo(self.mem[self.pc]) & 0b111)
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self.pc += 1
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if op == 0b110: # bdv
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self.reg[1] = self.reg[0] // (2**self._combo(self.mem[self.pc]))
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self.pc += 1
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if op == 0b111: # cdv
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self.reg[2] = self.reg[0] // (2**self._combo(self.mem[self.pc]))
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self.pc += 1
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def flush(self, binfmt = False):
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if not binfmt:
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print(','.join(map(str, self.outbuf)))
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else:
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for o in self.outbuf:
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print(f"{o:b},", end="")
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print()
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def cmp(self, prog):
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return self.outbuf == prog
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reg: array = array('q')
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mem: list = []
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pc: int = 0
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with open('day17') as f:
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reg_a = int(re.match('Register A: ([0-9]+)', f.readline()).groups()[0])
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reg_b = int(re.match('Register B: ([0-9]+)', f.readline()).groups()[0])
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reg_c = int(re.match('Register C: ([0-9]+)', f.readline()).groups()[0])
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reg = array('q', [reg_a, reg_b, reg_c])
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f.readline()
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mem_str = re.match('Program: (.*)', f.readline()).groups()[0]
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for c in mem_str:
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if c == ',': continue
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mem.append(int(c))
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vm = VM(reg, mem, pc)
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vm.run()
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vm.flush()
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# enumerates all 3 bit number, then increases size by one
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# enumerates them again
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#
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# don't know how exactly it enumerates but it enumerate
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# lower bytes before changing high byte
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# -> we can tighten boundaries ever more once we find
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# valid high bytes one after the other
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#
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# but first we need to find where to even start
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# we know the reg_a from the puzzle input is
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# too small, but start from here and increas rapidly:
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reg_a = 17323786
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while True:
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reg = array('q', [reg_a, reg_b, reg_c])
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vm = VM(reg, mem, pc)
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vm.run(abort=len(mem))
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if vm.cmp(mem): break
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# if reg_a % 1 == 0:
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# vm.flush(binfmt=True)
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if len(mem) == len(vm.outbuf): break
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reg_a *= 10
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print(reg_a)
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vm.flush()
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# well that was fast
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# we get: 173237860000000
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# producing a program: 4,4,4,4,1,6,0,0,0,2,1,0,0,1,3,0
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#
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# that's long enough and even better we even got the 2 highest bytes right
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# already
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# let's find our first set of boundaries so we can start a binary search
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known_bytes = vm.outbuf[-2:]
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init_reg_a = reg_a
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upper_bound = -1
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lower_bound = -1
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reg_a = init_reg_a
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while True:
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reg = array('q', [reg_a, reg_b, reg_c])
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vm = VM(reg, mem, pc)
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vm.run(abort=len(mem))
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if vm.cmp(mem): break
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if vm.outbuf[-2:] != known_bytes:
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upper_bound = reg_a
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break
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if len(vm.outbuf) > len(mem):
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upper_bound = reg_a
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break
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reg_a *= 10
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print(reg_a)
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vm.flush()
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reg_a = init_reg_a
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while True:
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reg = array('q', [reg_a, reg_b, reg_c])
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vm = VM(reg, mem, pc)
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vm.run(abort=len(mem))
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if vm.cmp(mem): break
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if vm.outbuf[-2:] != known_bytes:
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lower_bound = reg_a
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break
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if len(vm.outbuf) < len(mem):
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lower_bound = reg_a
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break
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reg_a //= 10
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print(reg_a)
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vm.flush()
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# that was fast again and did not produce very enlightening bounds,
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# nevertheless we have bounds
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#
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# ub: 1732378600000000
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# out: 4,4,0,7,0,7,6,0,3,5,1,5,4,2,4,4,2
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# lb: 17323786000000
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# 4,4,5,5,5,0,1,4,6,4,4,4,7,3,7
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