Towers of Hanoi move generator

hanoi_moves.py

def sol(n):
    other = lambda x: 1 if x == 2 else 2
    first, empty = (1, 2) if n % 2 == 0 else (2, 1)
    ms = [[1, 2, 0], [2, 0, 1]]
    m = ms[empty % 2]
    ret = [(0, first)]

    for i in xrange(2, n + 1):
        ret.append((0, empty))
        ret.extend(map(lambda x: (m[x[0]], m[x[1]]), ret[:-1]))
        empty = other(empty)
        m = ms[empty % 2]

    return ret