hanoi.py

#! /usr/bin/env python
# -*- coding:utf-8 -*-


def display_towers(towers):
    for i in range(3):
        tower_string = ', '.join(['{0:2d}'.format(num) for num in towers[i]])
        print 'tower {0} | {1}'.format(i, tower_string)
    print


def move_tower(from_pos, to_pos, height, towers):
    steps = 0
    if height == 1:                     # base case
        tmp = towers[from_pos].pop()
        towers[to_pos].append(tmp)
        display_towers(towers)
        steps += 1
    else:                               # recurse case
        tmp_to = [i for i in range(3) if i not in [from_pos, to_pos]][0]
        steps += move_tower(from_pos, tmp_to, height - 1, towers)
        steps += move_tower(from_pos, to_pos, 1, towers)
        steps += move_tower(tmp_to, to_pos, height - 1, towers)
    return steps


def solve_hanoi(height):
    if height < 1:
        print 'Error unexpected arguments exception'
        return 0
    towers = [
        [height - i for i in range(height)],
        [],
        []
    ]
    display_towers(towers)
    return move_tower(0, 2, height, towers)


if __name__ == '__main__':

    total_steps = solve_hanoi(5)

    if total_steps != 0:
        print 'total {0} steps'.format(total_steps)