Question

How to write a recursive function to generate all permutations of a string in Java

Answer 1

public class PermuteString {

    // Swap characters in a char array
    private static void swap(char[] arr, int i, int j) {
        char temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

    // Recursive function to generate permutations
    public static void generatePermutation(char[] str, int l, int r) {
        if (l == r) {
            System.out.println(new String(str));
        } else {
            for (int i = l; i <= r; i++) {
                swap(str, l, i);
                generatePermutation(str, l + 1, r);
                swap(str, l, i); // backtrack
            }
        }
    }

    public static void main(String[] args) {
        String s = "ABC";
        
        char[] chars = s.toCharArray();
        
        generatePermutation(chars, 0, chars.length - 1);
    }
}

  
  
/*
run:
  
ABC
ACB
BAC
BCA
CBA
CAB
  
*/

 

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