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Python Program to Print All Permutations of a String in Lexicographic Order using Recursion
When it is required to print all the permutations of a string in lexicographic order using recursion, a method is defined, that uses the ‘for’ loop to iterate over the sequence of elements, and use the ‘join’ method to join the elements.
Below is the demonstration of the same −
Example
from math import factorial
def lexicographic_permutation_order(s):
my_sequence = list(s)
for _ in range(factorial(len(my_sequence))):
print(''.join(my_sequence))
next = next_in_permutation(my_sequence)
if next is None:
my_sequence.reverse()
else:
my_sequence = next
def next_in_permutation(my_sequence):
if len(my_sequence) == 0:
return None
next = next_in_permutation(my_sequence[1:])
if next is None:
my_sequence[1:] = reversed(my_sequence[1:])
q = 1
while q < len(my_sequence) and my_sequence[0] > my_sequence[q]:
q += 1
if q == len(my_sequence):
return None
my_sequence[0], my_sequence[q] = my_sequence[q], my_sequence[0]
return my_sequence
else:
return [my_sequence[0]] + next
my_input = input('Enter a string : ')
print("The string is :")
print(my_input)
print("The method is being called...")
lexicographic_permutation_order(my_input)Output
Enter a string : hey The string is : hey The method is being called... hey hye yeh yhe hey hye
Explanation
The required packages are imported.
A method named ‘lexicographic_permutation_order’ is defined that helps find the lexicographic order of elements.
The method ‘next_in_permutation’ helps determine the next permutation in the string.
A string is entered by the user, and is displayed on the console.
The method is called by passing this string as a parameter.
The output is displayed on the console.
Updated on: 16-Apr-2021
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