Learn Recursion by Solving the Tower of Hanoi Puzzle - Step 23

Tell us what’s happening:

Isn’t that how I should check if rods[target] is empty or not?

Your code so far

NUMBER_OF_DISKS = 3
number_of_moves = 2**NUMBER_OF_DISKS - 1
rods = {
    'A': list(range(NUMBER_OF_DISKS, 0, -1)),
    'B': [],
    'C': []
}

def move(n, source, auxiliary, target):
    # display starting configuration
    print(rods)
    for i in range(number_of_moves):
        remainder = (i + 1) % 3

/* User Editable Region */

        if remainder == 1:
            print(f'Move {i + 1} allowed between {source} and {target}')
            forward = False

            if rods[target] == []: 
                # When target is empty, the disk should be moved necessarily from source to target
                forward = True

/* User Editable Region */

        elif remainder == 2:
            print(f'Move {i + 1} allowed between {source} and {auxiliary}')
        elif remainder == 0:
            print(f'Move {i + 1} allowed between {auxiliary} and {target}')

# initiate call from source A to target C with auxiliary B
move(NUMBER_OF_DISKS, 'A', 'B', 'C')

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Challenge Information:

Learn Recursion by Solving the Tower of Hanoi Puzzle - Step 23

Here you should not compare rods[target] with anything. Consider the code below:

if my_list:
    print('Hi')

When my_list is not empty, the condition of the if statement evaluates to True and Hi is printed. If you want to execute the if when the list is empty you need the condition evaluates to False. There’s an operator that does exactly this job.

1 Like

I tried using not, but it doesn’t work.

1 Like

Hello snigdho,

I would have to see your code with this change, but keep in mind if you use not you don’t need the == operator anymore.

def move(n, source, auxiliary, target):
    # display starting configuration
    print(rods)
    for i in range(number_of_moves):
        remainder = (i + 1) % 3
        if remainder == 1:
            print(f'Move {i + 1} allowed between {source} and {target}')
            forward = False

            if not rods[target]: 
                # When target is empty, the disk should be moved necessarily from source to target
                forward = True
        elif remainder == 2:
            print(f'Move {i + 1} allowed between {source} and {auxiliary}')

Here’s the code. BTW, please use “snigdho” if you are mentioning.

This should pass once you remove the comment.
If not you can reset the step and do it again to make sure you didn’t accidently touch anything else or have any magic spaces flying around.

4 Likes

You are right. Magic space. Thanks for the help.

3 Likes