归并排序

        /// <summary>
        /// 归并排序_合并
        /// </summary>
        /// <param name="v"></param>
        /// <param name="first"></param>
        /// <param name="mid"></param>
        /// <param name="last"></param>
        public static int[] Merger(int[] v, int first, int mid, int last)
        {
            Queue<int> tempV = new Queue<int>();
            int indexA, indexB;
            //设置indexA，并扫描subArray1 [first,mid]
            //设置indexB, 并扫描subArray2 [mid,last]
            indexA = first;
            indexB = mid;
            //在没有比较完两个子标的情况下，比较 v[indexA]和v[indexB]
            //将其中小的放到临时变量tempV中
            while (indexA < mid && indexB < last)
            {
                if (v[indexA] < v[indexB])
                {
                    tempV.Enqueue(v[indexA]);
                    indexA++;
                }
                else
                {
                    tempV.Enqueue(v[indexB]);
                    indexB++;
                }
            }
            //复制没有比较完子表中的元素
            while (indexA < mid)
            {
                tempV.Enqueue(v[indexA]);
                indexA++;
            }
            while (indexB < last)
            {
                tempV.Enqueue(v[indexB]);
                indexB++;
            }
            int index = 0;
            while (tempV.Count > 0)
            {
                v[first + index] = tempV.Dequeue();
                index++;
            }
            return v;
        }

        /// <summary>
        /// 归并算法
        /// 原理：把原始数组分成若干子数组,对每一个子数组进行排序,
        ///       继续把子数组与子数组合并,合并后仍然有序,直到全部合并完,形成有序的数组
        /// </summary>
        /// <param name="v"></param>
        /// <param name="first"></param>
        /// <param name="last"></param>
        public static int[] MergerSort(int[] v, int first, int last)
        {
            if (first + 1 < last)
            {
                int mid = (first + last) / 2;
                MergerSort(v, first, mid);  //数组前一半
                MergerSort(v, mid, last);   //数组后一半
                v = Merger(v, first, mid, last);  //合并子序列
            }
            return v;
        }