数据结构和算法基础之归并排序

        /// <summary>
        /// 归并排序
        /// </summary>
        public static  void MergetSort(int[] arry,int first,int end)
        {
            if(first<end)
            {
                int mid = (end + first) / 2;
                MergetSort(arry, first, mid);
                MergetSort(arry, mid+1, end);
                Merging(arry, first, mid, end);
            }
           
        }

        public static void Merging(int[] arry,int first,int mid,int end)
        {
            int[] tmp = new int[end - first + 1];
            int tmpIndex = 0;
            int start = first;
            int n = mid+1;
            while(start<=mid&&n<end)
            {
               if(arry[start]<arry[n])
                {
                    tmp[tmpIndex] = arry[start];
                    start++;
                    tmpIndex++;
                }else
                {
                    tmp[tmpIndex] = arry[n];
                    n++;
                    tmpIndex++;
                }
            }
            while (start <=mid)
            {
                tmp[tmpIndex] = arry[start];
                start++;
                tmpIndex++;
            }
            while (n<end)
            {
                tmp[tmpIndex] = arry[n];
                n++;
                tmpIndex++;
            }

            for ( tmpIndex = 0,start=first;start<end;tmpIndex++,start++ )
            {
                arry[start] = tmp[tmpIndex];
            }
        }

 时间复杂度：nlog(n)