# WAP to Find all the Permutations of a String

What We Are Learn:

Find all the Permutations of a String: The given Java program generates all possible permutations of a given input string and prints them comma-separated. For the input string “abc,” the output will be “abc,acb,bca,bac,cab,cba,” representing all the unique combinations of the characters in the input string.

### Find all the Permutations of a String

```package com.softwaretestingo.interviewprograms;
public class InterviewPrograms43
{
/*
* Input = “abc”;
* Output = abc,acb,bca,bac,cab,cba,
*/
public static void main(String[] args)
{
String str = "abc";
int n = str.length();
merge(str, 0, n - 1);
}
private static void merge(String str, int lb, int ub)
{
if (lb == ub)
System.out.print(str+",");
else
{
for (int i = lb; i <= ub; i++)
{
str = swap(str, lb, i);
merge(str, lb + 1, ub);
str = swap(str, lb, i);
}
}
}
public static String swap(String a, int i, int j)
{
char temp;
char[] ch = a.toCharArray();
temp = ch[i];
ch[i] = ch[j];
ch[j] = temp;
return String.valueOf(ch);
}
}```

Output

`abc,acb,bac,bca,cba,cab,`

Here’s a step-by-step explanation of the program:

1. Define the main method:
• The program starts executing from the main method.
2. Initialize the input string:
• The input string str is initialized with the value “abc.”
3. Calculate the length of the string:
• The length of the string n is calculated using the length method.
4. Call the merge method:
• The merge method is called to generate all the permutations of the input string.
• The method is called with the input string str, and the lower bound (lb) is set to 0, and the upper bound (ub) is set to n – 1.
5. Implement the merge method:
• The merge method uses recursion to generate all permutations of the input string.
• If the lower bound (lb) is equal to the upper bound (ub), it means that a single permutation is obtained, and it is printed followed by a comma.
• Otherwise, a loop runs from the lower bound (lb) to the upper bound (ub).
• In each iteration, the swap method is called to swap the characters at the lb and i indices of the string str.
• Then, the merge method is recursively called with the updated string and an incremented lower bound (lb + 1).
• After the recursion, the swap method is called again to restore the original order of characters.
6. Implement the swap method:
• The swap method takes a string a and two indices i and j as parameters.
• It converts the string a to a character array ch.
• Then, it swaps the characters at indices i and j using a temporary variable temp.
• Finally, it returns the updated string after the swap.

The program uses a recursive approach to generate all the possible permutations of the input string “abc” and prints them comma-separated. The output will be “abc,acb,bca,bac,cab,cba,” representing all the unique combinations of the characters in the input string.

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