Print all permutation of a string using ArrayList

Given a string str, the task is to print all the permutations of str. 
A permutation is an arrangement of all or part of a set of objects, with regard to the order of the arrangement. 
For instance, the words ‘bat’ and ‘tab’ represents two distinct permutation (or arrangements) of a similar three-letter word.

Examples:

Input: str = “abc” 
Output: abc acb bac bca cba cab

Input: str = “bat” 
Output: bat bta abt atb tba tab 

Approach: Write a recursive function that will generate all the permutations of the string. Terminating condition will be when the passed string is empty, in that case the function will return an empty ArrayList.

Below is the implementation of the above approach: 

C++

#include <bits/stdc++.h> // includes all standard libraries in one header
using namespace std;

// Utility function to print the contents
// of the vector
void printVector(vector<string> arrV)
{
  arrV.erase(remove(arrV.begin(), arrV.end(), ""), arrV.end());
  for (int i = 0; i < arrV.size(); i++)
    cout << arrV[i] << " ";
}

// Function to returns the vector which contains
// all the permutation of str
vector<string> getPermutation(string str)
{
  // If string is empty
  if (str.length() == 0) {

    // Return an empty vector
    vector<string> empty;
    empty.push_back("");
    return empty;
  }

  // Take first character of str
  char ch = str[0];

  // Take sub-string starting from the
  // second character
  string subStr = str.substr(1);

  // Recursive call
  vector<string> prevResult = getPermutation(subStr);

  // Store the generated permutations
  // into the resultant vector
  vector<string> Res;

  for (string val : prevResult) {
    for (int i = 0; i <= val.length(); i++) {
      Res.push_back(val.substr(0, i) + ch + val.substr(i));
    }
  }

  // Return the resultant vector
  return Res;
}

// Driver code
int main()
{
  string str = "abc";
  printVector(getPermutation(str));
  return 0;
}

Java

// Java implementation of the approach
import java.util.ArrayList;

public class GFG {

    // Utility function to print the contents
    // of the ArrayList
    static void printArrayList(ArrayList<String> arrL)
    {
        arrL.remove("");
        for (int i = 0; i < arrL.size(); i++)
            System.out.print(arrL.get(i) + " ");
    }

    // Function to returns the arraylist which contains
    // all the permutation of str
    public static ArrayList<String> getPermutation(String str)
    {

        // If string is empty
        if (str.length() == 0) {

            // Return an empty arraylist
            ArrayList<String> empty = new ArrayList<>();
            empty.add("");
            return empty;
        }

        // Take first character of str
        char ch = str.charAt(0);

        // Take sub-string starting from the
        // second character
        String subStr = str.substring(1);

        // Recursive call
        ArrayList<String> prevResult = getPermutation(subStr);

        // Store the generated permutations
        // into the resultant arraylist
        ArrayList<String> Res = new ArrayList<>();

        for (String val : prevResult) {
            for (int i = 0; i <= val.length(); i++) {
                Res.add(val.substring(0, i) + ch + val.substring(i));
            }
        }

        // Return the resultant arraylist
        return Res;
    }

    // Driver code
    public static void main(String[] args)
    {
        String str = "abc";
        printArrayList(getPermutation(str));
    }
}

Python3

from typing import List

# Function to returns the list which contains all the permutations of a string
def get_permutation(string: str) -> List[str]:

    # If string is empty
    if len(string) == 0:
        # Return an empty list
        return [""]

    # Take first character of str
    ch = string[0]

    # Take sub-string starting from the second character
    sub_str = string[1:]

    # Recursive call
    prev_result = get_permutation(sub_str)

    # Store the generated permutations into the resultant list
    res = []
    for val in prev_result:
        for i in range(len(val) + 1):
            res.append(val[:i] + ch + val[i:])

    # Return the resultant list
    return res

# Driver code
def main():
    string = "abc"
    print(get_permutation(string))

if __name__ == "__main__":
    main()

    # This code is contributed by mallelagowtalm.

C#

// C# implementation of the approach
using System.Collections.Generic;
using System;

class GFG
{

    // Utility function to print the contents
    // of the ArrayList
    static void printArrayList(List<String> arrL)
    {
        arrL.Remove("");
        for (int i = 0; i < arrL.Count; i++)
            Console.Write(arrL[i] + " ");
    }

    // Function to returns the arraylist which contains
    // all the permutation of str
    public static List<String> getPermutation(String str)
    {

        // If string is empty
        if (str.Length == 0)
        {

            // Return an empty arraylist
            List<String> empty = new List<String>();
            empty.Add("");
            return empty;
        }

        // Take first character of str
        char ch = str[0];

        // Take sub-string starting from the
        // second character
        String subStr = str.Substring(1);

        // Recursive call
        List<String> prevResult = getPermutation(subStr);

        // Store the generated permutations
        // into the resultant arraylist
        List<String> Res = new List<String>();

        foreach (String val in prevResult)
        {
            for (int i = 0; i <= val.Length; i++)
            {
                Res.Add(val.Substring(0, i) + ch + val.Substring(i));
            }
        }

        // Return the resultant arraylist
        return Res;
    }

    // Driver code
    public static void Main(String[] args)
    {
        String str = "abc";
        printArrayList(getPermutation(str));
    }
}

// This code has been contributed by 29AjayKumar

Javascript

<script>

// JavaScript implementation of the approach

// Utility function to print the contents
    // of the ArrayList
function printArrayList(arrL)
{

        for (let i = 0; i < arrL.length; i++)
            document.write(arrL[i] + " ");
}

// Function to returns the arraylist which contains
    // all the permutation of str
function getPermutation(str)
{
    // If string is empty
        if (str.length == 0) {

            // Return an empty arraylist
            let empty = [];
            empty.push("");
            return empty;
        }

        // Take first character of str
        let ch = str[0];

        // Take sub-string starting from the
        // second character
        let subStr = str.substring(1);

        // Recursive call
        let prevResult = getPermutation(subStr);

        // Store the generated permutations
        // into the resultant arraylist
        let Res = [];

        for (let val of prevResult) {
            for (let i = 0; i <= val.length; i++) {
                Res.push(val.substring(0, i) + ch + val.substring(i));
            }
        }

        // Return the resultant arraylist
        return Res;
}

// Driver code
let str = "abc";
printArrayList(getPermutation(str));

// This code is contributed by unknown2108

</script>

Output

abc bac bca acb cab cba 

Time Complexity: O(n*n!) 
Auxiliary Space: O(n)