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String Permutation in Python without itertools

Aniruddha Chaudhari/636/0
CodePython

Problem statement: Write a program to find all the permutations of the string in Python without itertools.

What is permutation?

A permutation is a technique that is used to determine all the strings obtained by rearranging the characters.

Example:

  • The permutations of string “ab” is [‘ab’, ‘ba’].
  • The permutations of string “abc” is [‘abc’, ‘acb’, ‘bac’, ‘bca’, ‘cba’, ‘cab’].

The number permutation that can be formed from the string is n! (n factorial). Where, n is the length of the given string.

Solution:

Here we are using recursion to get all the permutations of the string in Python.

Finding permutations in Python programming is very much easy using itertools Python module. But in competitive coding programming or coding interview, you have to use your own logic instead of using itertools.

Python code:

out=[]

def permute(msg, i, length):
    if i==length:
        out.append("".join(msg))
    else:
        for j in range(i, length):
            msg[i], msg[j] = msg[j], msg[i]
            permute(msg, i+1, length)
            msg[j], msg[i] = msg[i], msg[j]

msg="abc"
permute(list(msg), 0, len(msg))
print(out)

Function permute() takes Python list as input. So you have to convert the given string into list using list() function. Use the join() method to convert the list into the string.

Output:

['abc', 'acb', 'bac', 'bca', 'cba', 'cab']

This is the simple program you can write to get all the permutation in Python without itertools.

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Aniruddha Chaudhari
I am complete Python Nut, love Linux and vim as an editor. I hold a Master of Computer Science from NIT Trichy. I dabble in C/C++, Java too. I keep sharing my coding knowledge and my own experience on CSEstack.org portal.

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Why?

Why Competitive Programming Important?

Coding Challenges for Practice

  1. Count Common Factor
  2. Does it Divide
  3. Sum of Sub Arrays
  4. Pair of Desired Sum
  5. Remove Duplicate Char from String
  6. Sort String by Char Freq (Python)
  7. Sort String by Char Freq (Java)
  8. Split Array into Equal Sum Subarray
  9. Validate IP Address
  10. Validate PAN Card Number
  11. Validate Sudoku
  12. Sort Circular Rotated Array
  13. String Permutations
  14. Min Arrow to Burst Bubbles
  15. Min Cost to Paint All Houses [Amazon]
  16. HourGlass with Max Sum
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  20. Secure Conversation by Encry/Decry
  21. Special Elements in Matrix
  22. Next Greater No with Same set of Digits
  23. Smallest Subarray with Sum Greater than Given Number
  24. Group Anagrams
  25. Find Duplicates in Array in O(n)
  26. Find Two Unique Numbers from Array in O(n)
  27. Number Patterns & Finding Smallest Number
  28. First Unique Element in a Stream
  29. Flip Equivalent Binary Trees [TeachMint]
  30. Minimum Cost of Merging Files [Amazon]
  31. Minimum Distance for Truck to Deliver Order [Amazon]
  32. Longest Sequence of URLs
  33. Order Task for Given Dependencies
  34. Design Music Player
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  38. Max Avg Sum of Two Subsequences
  39. Merge Overlapping Intervals
  40. Longest Balanced Substring
  41. Longest Path in a Weighted Tree
  42. Generate Balanced Parentheses
  43. PostOrder Traversal Without Recursion

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