How to Find All Combinations of Items in a C# Array?

C# array element combination search method

This article explores various methods of finding combinations of all elements of an array in C#. Different techniques can be chosen depending on specific needs, such as whether duplication is allowed, the number of elements required in each combination, and the desired order.

Allow duplicate permutations

To find an array permutation that allows duplicate elements, use the GetPermutationsWithRept function. This method allows each element to be used multiple times in a composition. For example, for an array of length 2 {1, 2, 3, 4}, the output would be:

<code>{1,1} {1,2} {1,3} {1,4}
{2,1} {2,2} {2,3} {2,4}
{3,1} {3,2} {3,3} {3,4}
{4,1} {4,2} {4,3} {4,4}</code>

Duplicate arrangements are not allowed

If repetition is not required, use the GetPermutations function. This method limits each element to be used only once per combination. For the same array and length, the output would be:

<code>{1,2} {1,3} {1,4} 
{2,1} {2,3} {2,4} 
{3,1} {3,2} {3,4} 
{4,1} {4,2} {4,3} </code>

Duplicate K combinations allowed

To find K combinations of arrays that allow duplicate elements, use the GetKCombsWithRept function. This method allows each element to be used multiple times in a combination, the output will be:

<code>{1,1} {1,2} {1,3} {1,4} 
{2,2} {2,3} {2,4} 
{3,3} {3,4} 
{4,4} </code>

Duplicate K combinations are not allowed

If repetition is not required in K combinations, please use the GetKCombs function. This method ensures that each element in the combination is used only once. For the given array and length, the output will be:

<code>{1,2} {1,3} {1,4} 
{2,3} {2,4} 
{3,4} </code>

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