ArrayExtensionMethods.cs

using System.Collections.Generic;
using System.Linq;

namespace Kogane
{
    /// <summary>
    /// 配列の拡張メソッド
    /// </summary>
    public static class ArrayExtensionMethods
    {
        //================================================================================
        // 関数(static)
        //================================================================================
        /// <summary>
        /// 二次元配列のように扱っている一次元配列を時計回りに 90 度回転させたものを返します
        /// </summary>
        public static (T[] array, int newColumn, int newRow) RotateClockwise<T>
        (
            this IReadOnlyList<T> self,
            int                   column,
            int                   row,
            int                   rotateCount
        )
        {
            var array     = self.ToArray();
            var newColumn = column;
            var newRow    = row;

            for ( var i = 0; i < rotateCount; i++ )
            {
                ( array, newColumn, newRow ) = array.RotateClockwise( newColumn, newRow );
            }

            return ( array, newColumn, newRow );
        }

        /// <summary>
        /// 二次元配列のように扱っている一次元配列を時計回りに 90 度回転させたものを返します
        /// </summary>
        public static (T[] array, int newColumn, int newRow) RotateClockwise<T>
        (
            this IReadOnlyList<T> self,
            int                   column,
            int                   row
        )
        {
            var newColumn = row;
            var newRow    = column;
            var array     = new T[ column * row ];

            for ( var y = 0; y < row; y++ )
            {
                for ( var x = 0; x < column; x++ )
                {
                    var index    = x + y * column;
                    var newX     = row - 1 - y;
                    var newY     = x;
                    var newIndex = newX + newY * newColumn;

                    array[ newIndex ] = self[ index ];
                }
            }

            return ( array, newColumn, newRow );
        }
    }
}