hanoy.py

# execute like: python hanoi.py a b 5
from time import sleep

DO_SLEEP = False

class Hanoi:
    def __init__(self, pilon: str, height: int):
        self.pilons = {
            'a': [],
            'b': [],
            'c': [],
        }
        self.pilons[pilon] = list(range(height, 0, -1))

    def pretty(self):
        max_ring = max(max(p, default=0) for p in self.pilons.values())

        res = [f'{"A":^{max_ring}} ¦ {"B":^{max_ring}} ¦ {"C":^{max_ring}}',
                '=' * (3 * max_ring + 6)]
        for h in range(max_ring + 1):
            a, b, c = 0, 0, 0
            if h < len(self.pilons['a']):
                a = self.pilons['a'][h]
            if h < len(self.pilons['b']):
                b = self.pilons['b'][h]
            if h < len(self.pilons['c']):
                c = self.pilons['c'][h]
            res += [f'{"-" * a:^{max_ring}} ¦ {"-" * b:^{max_ring}} ¦ {"-" * c:^{max_ring}}']
        print('\033[2J\033[H' + '\n'.join(reversed(res + [''])))

    def invariant(self):
        if not all(all(pilon[i] > pilon[i+1] for i in range(len(pilon)-1)) for pilon in self.pilons.values()):
            print('ERROR' + str(self))
            raise Exception()

    def move(self, src, tgt):
        self.pilons[tgt].append(self.pilons[src].pop())
        self.invariant()


def move(hanoi, src, tgt, other, lvl=0):
    # lvl indicates on which level we are operating right now

    # we might have to move the rings above me to the other pilon
    has_rings_above = len(hanoi.pilons[src]) > lvl + 1
    if has_rings_above:
        other_height = len(hanoi.pilons[other])
        move(hanoi, src, other, tgt, lvl + 1)

    # move this ring to the target
    hanoi.move(src, tgt)
    hanoi.pretty()
    if DO_SLEEP:
        sleep(.5)

    # move the rings, that were above me previously, back ontop of me
    if has_rings_above:
        move(hanoi, other, tgt, src, other_height)


if __name__ == "__main__":
    import sys

    # arguments: python hanoi.py a b 5
    src = sys.argv[1]
    tgt = sys.argv[2]
    height = int(sys.argv[3])
    DO_SLEEP = height < 10
    h = Hanoi(src, height)

    others = h.pilons.keys() - {src, tgt}
    assert len(others) == 1
    other = others.pop()

    # do the moving
    h.pretty()
    move(h, src, tgt, other)