Merge Sort

实现如下：

 

        #region Merge Sort
        private static void Merge(int[] data, int startIndex1, int endIndex1, int startIndex2, int endIndex2)
        {
            if (data == null || data.Length < 1)
            {
                throw new ArgumentNullException("data");
            }
            if (startIndex1 < 0 || startIndex2 < 0 || endIndex1 < startIndex1 || endIndex2 < startIndex2 ||
                endIndex1 > data.Length || endIndex2 > data.Length)
            {
                throw new ArgumentException("index");
            }

            int[] tempArray = new int[endIndex1 - startIndex1 + endIndex2 - startIndex2 + 2];
            int index1 = startIndex1, index2 = startIndex2;
            int tempIndex = 0;
            while(index1 <= endIndex1 && index2 <= endIndex2)
            {
                if (data[index1] <= data[index2])
                {
                    tempArray[tempIndex++] = data[index1++];
                }
                else
                {
                    tempArray[tempIndex++] = data[index2++];
                }
            }

            while (index1 <= endIndex1)
            {
                tempArray[tempIndex++] = data[index1++];
            }
            while (index2 <= endIndex2)
            {
                tempArray[tempIndex++] = data[index2++];
            }

            tempIndex = 0;
            for (int i = startIndex1; i <= endIndex1; i++)
            {
                data[i] = tempArray[tempIndex++];
            }
            for (int i = startIndex2; i <= endIndex2; i++)
            {
                data[i] = tempArray[tempIndex++];
            }
        }

        private static void MergePass(int[] data, int cellLength)
        {
            if (data == null || data.Length < 1)
            {
                throw new ArgumentNullException("data");
            }
            if (cellLength < 1 || cellLength > data.Length)
            {
                throw new ArgumentException("cellLength");
            }

            int index = 0;
            while (index <= data.Length - cellLength * 2)
            {
                Merge(data, index, index + cellLength - 1, index + cellLength, index + cellLength * 2 - 1);
                index += 2 * cellLength;
            }
            if (index + cellLength < data.Length)
            {
                Merge(data, index, index + cellLength - 1, index + cellLength, data.Length - 1);
            }
        }

        /// <summary>
        /// 二路归并排序
        /// </summary>
        /// <param name="data"></param>
        public static void MergeSort(int[] data)
        {
            if (data == null || data.Length < 1)
            {
                throw new ArgumentNullException("data");
            }

            int cellLength = 1;
            while (cellLength < data.Length)
            {
                MergePass(data, cellLength);
                cellLength *= 2;
            }
        }
        #endregion