Python, fait maison

Bon, fait maison, c'est à dire sans eval ni bibliothèque externe. On construit un arbre, pour la première partie on calcule récursivement la valeur du singe racine. Pour la deuxième partie, on force la valeur du singe racine, ce qui force récursivement la valeur des singes en-dessous, jusqu'à forcer la valeur de l'humain.

from __future__ import annotations
import re
from collections import defaultdict
from enum import Enum
from typing import Callable, Dict, Iterable, Optional, Sequence, Set, Tuple
class Operation(Enum):
 ADD = '+'
 SUB = '-'
 MUL = '*'
 DIV = '/'
 @property
 def op(self) -> Callable[[int, int], int]:
 if self is self.ADD:
 return int.__add__
 if self is self.SUB:
 return int.__sub__
 if self is self.MUL:
 return int.__mul__
 if self is self.DIV:
 return int.__floordiv__
 assert False # we covered all cases
 @property
 def rev1(self) -> Callable[[int, int], int]:
 """Given a and b, return x so self.op(x, a) = b"""
 if self is self.ADD:
 return int.__sub__
 if self is self.SUB:
 return int.__add__
 if self is self.MUL:
 return int.__floordiv__
 if self is self.DIV:
 return int.__mul__
 assert False # we covered all cases
 @property
 def rev2(self) -> Callable[[int, int], int]:
 """Given a and b, return x so self.op(a, x) = b"""
 if self is self.ADD:
 return int.__sub__
 if self is self.SUB:
 return lambda v, a: a - v
 if self is self.MUL:
 return int.__floordiv__
 if self is self.DIV:
 return lambda v, a: a // v
 assert False # we covered all cases
class Monkey:
 monkeys: Dict[str, Monkey] = {}
 def __init__(self, name: str,
 value: Optional[int] = None,
 others: Optional[Sequence[str]] = None,
 operation: Optional[Operation] = None) -> None:
 if (others is None) != (operation is None):
 raise ValueError(
 "others and operation must be both None or both defined")
 if (value is None) == (others is None):
 raise ValueError(
 "value xor (others and operation) must be defined")
 self.name = name
 self._value = value
 self.others = others
 self.operation = operation
 # Register self in class directory
 self.monkeys[name] = self
 @property
 def value(self) -> int:
 if self._value is not None:
 return self._value
 if self.others is None or self.operation is None:
 raise ValueError(
 "cannot compute value of a monkey w/o others or operation")
 return self.operation.op(
 *[self.monkeys[other].value for other in self.others])
 @value.setter
 def value(self, v: int) -> None:
 if self._value is not None:
 # This monkey has a fixed value
 raise ValueError("cannot change value of a valued monkey")
 if self.others is None or self.operation is None:
 # This monkey has a free value, we just have to set it
 self._value = v
 return
 # The free monkey is somewhere under self
 a: Optional[int] = None # value of first sub-monkey
 b: Optional[int] = None # value of second sub-monkey
 try:
 a = self.monkeys[self.others[0]].value
 except ValueError:
 # This failed because the value-free monkey is here, not a problem
 pass
 try:
 b = self.monkeys[self.others[1]].value
 except ValueError:
 # This failed because the value-free monkey is here, not a problem
 pass
 if a is None and b is not None:
 a = self.operation.rev1(v, b)
 self.monkeys[self.others[0]].value = a
 return
 if a is not None and b is None:
 b = self.operation.rev2(v, a)
 self.monkeys[self.others[1]].value = b
 return
 # We do not expect to have two or no value-free monkey under us
 assert False
 _monkey_re = re.compile(r"^(\w+): (.*)\n?$")
 _operation_re = re.compile(r"^(\w+) ([-+/*]) (\w+)\n?$")
 @classmethod
 def import_line(class_, line: str) -> Monkey:
 match = class_._monkey_re.match(line)
 if match is None:
 raise ValueError("invalid monkey description '{}'".format(line))
 name = match.group(1)
 line = match.group(2)
 if line.isdigit():
 value = int(line)
 return class_(name, value=value)
 match = class_._operation_re.match(line)
 if match is None:
 raise ValueError("invalid monkey operation '{}'".format(line))
 others = (match.group(1), match.group(3))
 op = Operation(match.group(2))
 return class_(name, others=others, operation=op)
def solve_both(lines: Iterable[str]) -> Tuple[int, int]:
 """Solve both parts of today's puzzle"""
 for line in lines:
 _ = Monkey.import_line(line)
 root = Monkey.monkeys['root']
 humn = Monkey.monkeys['humn']
 # Get original root monkey value
 result1 = root.value
 # Correct root monkey operation
 root.operation = Operation.SUB
 # Unset our own value so it becomes the free one
 humn._value = None
 # Force root monkey value: this will cascade to eventually set
 # our value
 root.value = 0
 result2 = humn.value
 return result1, result2