CODEWITHSUNDEEP
.netmathcombinationspermutation
activebiz
activebiz

Reputation: 6230

Combinations from an array in .NET

I am not sure if this question is for Maths section or for this one but I need a programmatic solution (in .NET) hence I am placing the question here.

I have an array with variable length which outputs as shown in below example.

for int[] arr = {1,2} it would be as follows:

[1 , 2],[1],[2]

for int[] arr = {1,2,3} it would be as follows:

[1 , 2],[2 , 3],[3 , 1],[1],[2],[3],[1 , 2 , 3]

for int[] arr = {1,2,3,4} it would be like

[1 , 2],[2 , 3],[3 , 4],[4 , 1],[1],[2],[3],[4],[1,2,3],[2,3,4],[3,4,1],[4,1,2],[1,2,3,4]

for int[] arr = {1,2,3,4,5} .....

I think you should be able to see the pattern by now

Any pointers or hints how to solve this programmatically or any if there a related mathematical formula that anyone can think of?

Thanks,

Upvotes: 0

Views: 72

Answers (1)

xanatos
xanatos

Reputation: 111860

I think it's quite useless as a program, and as an exercise if you don't do it yourself then it's useless. But I give everyone what they ask...

int[] arr = new int[] { 1, 2, 3 };

// How much elements in each permutation
for (int i = 1; i <= arr.Length; i++)
{
    // Starting point of the permutation
    for (int j = 0; j < arr.Length; j++)
    {
        Console.Write("[");

        // Single element of the permutation
        for (int k = 0; k < i; k++)
        {
            if (k != 0)
            {
                Console.Write(", ");
            }

            Console.Write("{0}", arr[(j + k) % arr.Length]);
        }

        Console.WriteLine("]");

        // Single cycle for last permutation of length arr.Length
        if (i == arr.Length)
        {
            break;
        }
    }
}

Upvotes: 2

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