Tower of Hanoi Python

In this post, you will learn the Tower of Hanoi program using the Python programming language.

The Tower of Hanoi is a mathematical puzzle containing 3 pillars/towers with n disks each of a different size/diameter.

Given a stack of n disks arranged from biggest on the bottom to smallest on top put on a rod, along with two empty rods, the tower of Hanoi puzzle asks for the minimum number of moves required to move the stack from one rod to another, where moves are allowed only if they place smaller disks on the top of bigger disks.

Rules of Tower of Hanoi Problem

The rules for this puzzle are-

1. We can move only one disk at a time.
2. We can remove only the top disk.
3. We can only place a disk above a disk of a bigger size.

Python Program for Tower of Hanoi Problem Using Recursion

Here, the function tower_of_hanoi() calls recursively and outputs a sequence of steps to move n disks from the start rod to the end rod.

# Creating a recursive function  
def tower_of_hanoi(disks, source, auxiliary, destination):  
    if(disks == 1):  
        print('Move disk 1 from rod {} to rod {}.'.format(source, destination))  
        return  
    
    # calling recursion function
    tower_of_hanoi(disks - 1, source, destination, auxiliary)  
    print('Move disk {} from rod {} to rod {}.'.format(disks, source, destination))  
    tower_of_hanoi(disks - 1, auxiliary, source, destination)  
  
  
disks = int(input('Enter the number of disks: '))  
# Calling the function 
# Here, we are passing source as A, auxiliary as B, and destination as C  
tower_of_hanoi(disks, 'A', 'B', 'C')   

Enter the number of disks: 
3
Move disk 1 from rod A to rod C.
Move disk 2 from rod A to rod B.
Move disk 1 from rod C to rod B.
Move disk 3 from rod A to rod C.
Move disk 1 from rod B to rod A.
Move disk 2 from rod B to rod C.
Move disk 1 from rod A to rod C.

Enter the number of disks: 
4
Move disk 1 from rod A to rod B.
Move disk 2 from rod A to rod C.
Move disk 1 from rod B to rod C.
Move disk 3 from rod A to rod B.
Move disk 1 from rod C to rod A.
Move disk 2 from rod C to rod B.
Move disk 1 from rod A to rod B.
Move disk 4 from rod A to rod C.
Move disk 1 from rod B to rod C.
Move disk 2 from rod B to rod A.
Move disk 1 from rod C to rod A.
Move disk 3 from rod B to rod C.
Move disk 1 from rod A to rod B.
Move disk 2 from rod A to rod C.
Move disk 1 from rod B to rod C.

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