Python | Permutation of a given string using inbuilt function

The task is to generate all the possible permutations of a given string. A permutation of a string is a rearrangement of its characters. For example, the permutations of “ABC” are “ABC”, “ACB”, “BAC”, “BCA”, “CAB”, and “CBA”. The number of permutations of a string with n unique characters is n! (factorial of n).

We can generate permutations of a string in Python using methods like inbuilt functions and recursion.

Using itertools.permutations

itertools module in Python provides a simple function called permutations that can generate all possible permutations of a string. This method is the easiest and most efficient, especially when working with built-in Python libraries.

import itertools

s = "GFG"
li = [''.join(p) for p in itertools.permutations(s)]
print(li)

Explanation:

• itertools.permutations(s) generates all possible permutations of the string s, returning each permutation as a tuple.
• ”.join(p) converts each tuple p into a string by concatenating its elements.
• list comprehension collects all the joined strings (permutations) into a list.

Using Recursion

Recursion is a method where a function calls itself to solve smaller parts of a problem. In the case of generating permutations, we can break down the problem by selecting one character at a time and recursively permuting the rest of the string. This approach is a bit more complex than using itertools.permutations, but it can be useful if we want more control over the process.

def permute(s, s2):
    if len(s) == 0:
        print(s2, end=' ')
        return
    
    for i in range(len(s)):
        char = s[i]
        left_s = s[0:i]
        right_s = s[i+1:]
        rest = left_s + right_s
        permute(rest, s2 + char)

s1 = "GFG"
s2 = ""
permute(s1, s2)

GFG GGF FGG FGG GGF GFG 

Explanation:

• If the string s is empty, print the accumulated answer.
• For each character in s, remove the character and recursively permute the remaining characters while adding the character to answer.
• Call permute(s, answer) with the initial string and an empty answer to start generating permutations.