AoC Day 21

import pathlib
import operator

ops = {'+': operator.add, '-': operator.sub, '*': operator.mul, '/': operator.floordiv}

with pathlib.Path("day21.txt").open('r') as f:
    known, known2, unknown = {}, {}, []
    for k, v in (l.strip().split(": ", 1) for l in f.readlines()):
        if len(bits := v.split(' ')) == 1:
            known2[k] = known[k] = int(v)
        else:
            unknown.append((k, bits[0], ops[bits[1]], bits[2]))

while unknown:
    for _ in range(len(unknown)):
        k, m1, op, m2 = r = unknown.pop(0)
        if m1 not in known or m2 not in known:
            unknown.append(r)
            continue

        known[k] = int(op(known[m1], known[m2]))

        if k == 'root':
            known2[k] = (known2[m1], known2[m2])
        elif 'humn' not in (m1, m2) and isinstance(known2[m1], int) and isinstance(known2[m2], int):
            known2[k] = known[k]
        else:
          known2[k] = (op, 'x' if m1 == 'humn' else known2[m1], 'x' if m2 == 'humn' else known2[m2])

print(known['root'])

l, r = known2['root']
if isinstance(r, int): # one of l and r is literal - make sure it is l
    t = r; r = l; l = t # swap r and l

while r: # reverse the equation to solve for x
    if r == 'x': break # we're done!
    fn, a, b = r
    r = a if isinstance(b, int) else b # keep expanding into which ever of a and b is a tuple
    # rearrange the current level of the equation to put the tuple on the right
    if fn == operator.floordiv: # l = a / b
        l = l*b if isinstance(b, int) else a / l
    elif fn == operator.mul: # l = a * b
        l = int(l / (a  if isinstance(a, int) else b))
    elif fn == operator.sub: # l = a - b
        l = a-l if isinstance(a, int) else l+b
    else: # l = a + b
        l = l - (a if isinstance(a, int) else b)

print(l)