Question

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

Answer 1

using System;

class PermuteString
{
    // Swap characters in a char array
    static void Swap(ref char a, ref char b) {
        char temp = a;
        a = b;
        b = temp;
    }

    // Recursive function to generate permutations
    static void generatePermutation(char[] str, int l, int r) {
        if (l == r) {
            Console.WriteLine(new string(str));
        }
        else 
        {
            for (int i = l; i <= r; i++) {
                Swap(ref str[l], ref str[i]);
                generatePermutation(str, l + 1, r);
                Swap(ref str[l], ref str[i]); // backtrack
            }
        }
    }

    static void Main()
    {
        string s = "ABC";
        
        char[] chars = s.ToCharArray();
        
        generatePermutation(chars, 0, chars.Length - 1);
    }
}


 
 
/*
run:

ABC
ACB
BAC
BCA
CBA
CAB
 
*/

 

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