print all permutations of a given string

http://www.geeksforgeeks.org/write-a-c-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! permutation.
Source: Mathword(http://mathworld.wolfram.com/Permutation.html)

Below are the permutations of string ABC.
ABC, ACB, BAC, BCA, CAB, CBA

Here is a solution using backtracking.

//c# code
public static class Permutation
    {
        //static void Main(string[] args)
        //{
        //    char[] s = new char[] { 'a', 'b', 'c' };
        //    Permutation.permutate(ref s, 0, 3);

        //    Console.Read();
        //}

        public static void swap(ref char a, ref char b)
        {
            char tmp;
            tmp = a;
            a = b;
            b = tmp;
        }
        //   1. String
        //   2. Starting index of the string
        //   3. Ending index of the string. */
        public static void permutate(ref char[] sArray,int i,int n)
        {
            int j = 0;
            if (i ==n)
            {
                Console.WriteLine(sArray);
            }
            else
            {
                for (j = i; j < n; j++)
                {
                    Permutation.swap(ref sArray[i],ref sArray[j]);
                    Permutation.permutate(ref sArray, i + 1, n);
                    Permutation.swap(ref sArray[i], ref sArray[j]);
                }
            }

        }
    }

Algorithm Paradigm: Backtracking
Time Complexity: O(n*n!)