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Sorting a Two-Dimensional Array in C#

, 16 Mar 2011 CPOL
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How to sort a two-dimensional array in C#

I'm a fan of Linq and extension methods for things like this. So, how does this look to you?

public static class MultiDimensionalArrayExtensions
{
  /// <summary>
  ///   Orders the two dimensional array by the provided key in the key selector.
  /// </summary>
  /// <typeparam name="T">The type of the source two-dimensional array.</typeparam>
  /// <param name="source">The source two-dimensional array.</param>
  /// <param name="keySelector">The selector to retrieve the column to sort on.</param>
  /// <returns>A new two dimensional array sorted on the key.</returns>
  public static T[,] OrderBy<T>(this T[,] source, Func<T[], T> keySelector)
  {
      return source.ConvertToSingleDimension().OrderBy(keySelector).ConvertToMultiDimensional();
  }
  /// <summary>
  ///   Orders the two dimensional array by the provided key in the key selector in descending order.
  /// </summary>
  /// <typeparam name="T">The type of the source two-dimensional array.</typeparam>
  /// <param name="source">The source two-dimensional array.</param>
  /// <param name="keySelector">The selector to retrieve the column to sort on.</param>
  /// <returns>A new two dimensional array sorted on the key.</returns>
  public static T[,] OrderByDescending<T>(this T[,] source, Func<T[], T> keySelector)
  {
      return source.ConvertToSingleDimension().
      	OrderByDescending(keySelector).ConvertToMultiDimensional();
  }
  /// <summary>
  ///   Converts a two dimensional array to single dimensional array.
  /// </summary>
  /// <typeparam name="T">The type of the two dimensional array.</typeparam>
  /// <param name="source">The source two dimensional array.</param>
  /// <returns>The repackaged two dimensional array as a single dimension based on rows.</returns>
  private static IEnumerable<T[]> ConvertToSingleDimension<T>(this T[,] source)
  {
      T[] arRow;
 
      for (int row = 0; row < source.GetLength(0); ++row)
      {
          arRow = new T[source.GetLength(1)];
 
          for (int col = 0; col < source.GetLength(1); ++col)
              arRow[col] = source[row, col];
 
          yield return arRow;
      }
  }
  /// <summary>
  ///   Converts a collection of rows from a two dimensional array back into a two dimensional array.
  /// </summary>
  /// <typeparam name="T">The type of the two dimensional array.</typeparam>
  /// <param name="source">The source collection of rows to convert.</param>
  /// <returns>The two dimensional array.</returns>
  private static T[,] ConvertToMultiDimensional<T>(this IEnumerable<T[]> source)
  {
      T[,] twoDimensional;
      T[][] arrayOfArray;
      int numberofColumns;
 
      arrayOfArray = source.ToArray();
      numberofColumns = (arrayOfArray.Length > 0) ? arrayOfArray[0].Length : 0;
      twoDimensional = new T[arrayOfArray.Length, numberofColumns];
 
      for (int row = 0; row < arrayOfArray.GetLength(0); ++row)
          for (int col = 0; col < numberofColumns; ++col)
              twoDimensional[row, col] = arrayOfArray[row][col];
 
      return twoDimensional;
  }
}

Then, to be able to use the code above, you would simply do something like the following:

int[,] array = new int[3, 3] { { 1, 4, 2 }, { 4, 5, 1 }, { 7, 3, 8 } };
 
int[,] sortedByFirstElement = array.OrderBy(x => x[0]);
int[,] sortedBySecondElement = array.OrderBy(x => x[1]);
int[,] sortedByThirdElement = array.OrderBy(x => x[2]);

The keyselector Func is merely the way to determine the column to sort on using lambdas.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Andrew Rissing
Software Developer (Senior)
United States United States
Since I've begun my profession as a software developer, I've learned one important fact - change is inevitable. Requirements change, code changes, and life changes.
 
So..If you're not moving forward, you're moving backwards.

Comments and Discussions

 
GeneralReason for my vote of 5 Elegant solution, though not as tran... PinmemberDrABELL9-Apr-11 13:45 
GeneralI would like to see an example of how one would implement th... PinmemberTony Zackin10-Mar-11 17:42 
I would like to see an example of how one would implement this, specifically the "keySelector" function. Your alternative, which might be more efficient, is certainly not as obvious nor straightforward as the one I have instantiated.
GeneralRe: While I haven't tested it for performance, it may very well ... PinmemberAndrew Rissing11-Mar-11 5:14 
GeneralRe: Thanks for pointing out the extra ToArray. I have removed it... PinmemberAndrew Rissing16-Mar-11 10:12 

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