day7

day7.py

from collections import namedtuple
import copy

Gate = namedtuple('Gate', 'op in1 in2 out')
gates = set() # gates that have not been calculated yet
wires = {} # identifier -> value

def get_value(gate_in):
    if gate_in is None:
        return None
    try:
        return int(gate_in)
    except ValueError:
        return wires.get(gate_in)

def simulate():
    for gate in copy.copy(gates):
        val1 = get_value(gate.in1)
        val2 = get_value(gate.in2)
        if (gate.op is None or gate.op == 'NOT') and val1 is not None:
            if gate.op is None:
                wires[gate.out] = val1
            else: # NOT
                wires[gate.out] = 65535 - val1
            gates.remove(gate)
        elif val1 is not None and val2 is not None: # 2-arg OP
            if gate.op == 'AND':
                wires[gate.out] = val1 & val2
            elif gate.op == 'OR':
                wires[gate.out] = val1 | val2
            elif gate.op == 'LSHIFT':
                wires[gate.out] = val1 << val2
            elif gate.op == 'RSHIFT':
                wires[gate.out] = val1 >> val2
            gates.remove(gate)

with open('input7.txt') as f:
    for line in f:
        fragments = line.strip().split()
        if len(fragments) == 5:
            gate = Gate(fragments[1], fragments[0], fragments[2], fragments[4])
        elif len(fragments) == 4:
            gate = Gate(fragments[0], fragments[1], None, fragments[3])
        elif len(fragments) == 3:
            gate = Gate(None, fragments[0], None, fragments[2])
        gates.add(gate)

while wires.get('a') is None:
    simulate()

print(wires['a'])