Given a string S, the task is to write a program to print all permutations of a given string.
A permutation also called an “arrangement number” or “order,” is a rearrangement of the elements of an ordered list S into a one-to-one correspondence with S itself. A string of length N has N! permutations.
Examples:
Input: S = “ABC”
Output: “ABC”, “ACB”, “BAC”, “BCA”, “CBA”, “CAB”Input: S = “XY”
Output: “XY”, “YX”
Print permutations of a given string using backtracking:
Follow the given steps to solve the problem:
- Create a function permute() with parameters as input string, starting index of the string, ending index of the string
-
Call this function with values input string, 0, size of string – 1
-
In this function, if the value of L and R is the same then print the same string
- Else run a for loop from L to R and swap the current element in the for loop with the inputString[L]
- Then again call this same function by increasing the value of L by 1
- After that again swap the previously swapped values to initiate backtracking
-
In this function, if the value of L and R is the same then print the same string
Below is the implementation of the above approach:
// C++ program to print all // permutations with duplicates allowed #include <bits/stdc++.h> using namespace std;
// Function to print permutations of string // This function takes three parameters: // 1. String // 2. Starting index of the string // 3. Ending index of the string. void permute(string& a, int l, int r)
{ // Base case
if (l == r)
cout << a << endl;
else {
// Permutations made
for ( int i = l; i <= r; i++) {
// Swapping done
swap(a[l], a[i]);
// Recursion called
permute(a, l + 1, r);
// backtrack
swap(a[l], a[i]);
}
}
} // Driver Code int main()
{ string str = "ABC" ;
int n = str.size();
// Function call
permute(str, 0, n - 1);
return 0;
} // This is code is contributed by rathbhupendra |
// C program to print all permutations with duplicates // allowed #include <stdio.h> #include <string.h> /* Function to swap values at two pointers */ void swap( char * x, char * y)
{ char temp;
temp = *x;
*x = *y;
*y = temp;
} /* Function to print permutations of string This function takes three parameters: 1. String 2. Starting index of the string 3. Ending index of the string. */ void permute( char * a, int l, int r)
{ int i;
if (l == r)
printf ( "%s\n" , a);
else {
for (i = l; i <= r; i++) {
swap((a + l), (a + i));
permute(a, l + 1, r);
swap((a + l), (a + i)); // backtrack
}
}
} /* Driver code */ int main()
{ char str[] = "ABC" ;
int n = strlen (str);
permute(str, 0, n - 1);
return 0;
} |
// Java program to print all permutations of a // given string. public class Permutation {
// Function call
public static void main(String[] args)
{
String str = "ABC" ;
int n = str.length();
Permutation permutation = new Permutation();
permutation.permute(str, 0 , n - 1 );
}
/**
* permutation function
* @param str string to calculate permutation for
* @param l starting index
* @param r end index
*/
private void permute(String str, int l, int r)
{
if (l == r)
System.out.println(str);
else {
for ( int i = l; i <= r; i++) {
str = swap(str, l, i);
permute(str, l + 1 , r);
str = swap(str, l, i);
}
}
}
/**
* Swap Characters at position
* @param a string value
* @param i position 1
* @param j position 2
* @return swapped string
*/
public String swap(String a, int i, int j)
{
char temp;
char [] charArray = a.toCharArray();
temp = charArray[i];
charArray[i] = charArray[j];
charArray[j] = temp;
return String.valueOf(charArray);
}
} // This code is contributed by Mihir Joshi |
# Python3 program to print all permutations with # duplicates allowed def toString( List ):
return ''.join( List )
# Function to print permutations of string # This function takes three parameters: # 1. String # 2. Starting index of the string # 3. Ending index of the string. def permute(a, l, r):
if l = = r:
print (toString(a))
else :
for i in range (l, r):
a[l], a[i] = a[i], a[l]
permute(a, l + 1 , r)
a[l], a[i] = a[i], a[l] # backtrack
# Driver code string = "ABC"
n = len (string)
a = list (string)
# Function call permute(a, 0 , n)
# This code is contributed by Bhavya Jain |
// C# program to print all // permutations of a given string. using System;
class GFG {
/**
* permutation function
* @param str string to
calculate permutation for
* @param l starting index
* @param r end index
*/
private static void permute(String str, int l, int r)
{
if (l == r)
Console.WriteLine(str);
else {
for ( int i = l; i <= r; i++) {
str = swap(str, l, i);
permute(str, l + 1, r);
str = swap(str, l, i);
}
}
}
/**
* Swap Characters at position
* @param a string value
* @param i position 1
* @param j position 2
* @return swapped string
*/
public static String swap(String a, int i, int j)
{
char temp;
char [] charArray = a.ToCharArray();
temp = charArray[i];
charArray[i] = charArray[j];
charArray[j] = temp;
string s = new string (charArray);
return s;
}
// Driver Code
public static void Main()
{
String str = "ABC" ;
int n = str.Length;
permute(str, 0, n - 1);
}
} // This code is contributed by mits |
<script> // Javascript program to print all permutations of a // given string. function permute(str, l, r)
{ if (l == r)
document.write(str+ "<br>" );
else
{
for (let i = l; i <= r; i++)
{
str = swap(str, l, i);
permute(str, l + 1, r);
str = swap(str, l, i);
}
}
} function swap(a, i, j)
{ let temp;
let charArray = a.split( "" );
temp = charArray[i] ; charArray[i] = charArray[j]; charArray[j] = temp; return (charArray).join( "" );
} let str = "ABC" ;
let n = str.length; permute(str, 0, n-1); // This code is contributed by avanitrachhadiya2155 </script> |
<?php // PHP program to print all // permutations of a given string. /** * permutation function * @param str string to * calculate permutation for * @param l starting index * @param r end index */ function permute( $str , $l , $r )
{ if ( $l == $r )
echo $str . "\n" ;
else
{
for ( $i = $l ; $i <= $r ; $i ++)
{
$str = swap( $str , $l , $i );
permute( $str , $l + 1, $r );
$str = swap( $str , $l , $i );
}
}
} /** * Swap Characters at position * @param a string value * @param i position 1 * @param j position 2 * @return swapped string */ function swap( $a , $i , $j )
{ $temp ;
$charArray = str_split ( $a );
$temp = $charArray [ $i ] ;
$charArray [ $i ] = $charArray [ $j ];
$charArray [ $j ] = $temp ;
return implode( $charArray );
} // Driver Code $str = "ABC" ;
$n = strlen ( $str );
permute( $str , 0, $n - 1);
// This code is contributed by mits. ?> |
ABC ACB BAC BCA CBA CAB
Time Complexity: O(N * N!) Note that there are N! permutations and it requires O(N) time to print a permutation.
Auxiliary Space: O(R – L)
Note: The above solution prints duplicate permutations if there are repeating characters in the input string. Please see the below link for a solution that prints only distinct permutations even if there are duplicates in input.
- Print all distinct permutations of a given string with duplicates.
- Permutations of a given string using STL