归并排序

    class Program
    {
        static void Main(string[] args)
        {
            int[] arr = arrInsert(100000);
            merge_sort(arr,0,arr.Length-1);

        }
        static int[] arrInsert(int count)
        { 
            int[] arr=new int[count];
            Random r1=new Random();
            int i=0;
            while(i<count)
            {
              int num=r1.Next(0,10000); 
                arr[i]=num;
                i++;
            }
            return arr;
        }
        static void merge(int[] arr, int L, int M, int R)
        {
            int left_size = M-L;    //左半部分数组的长度
            int right_size = R-M+1;  //右半部分数组的长度
            int[] L_arr = new int[left_size];   //声明数组
            int[] R_arr = new int[right_size];  
            int i = 0, j = 0, k = 0;

            for ( i = L; i < M; i++)  //数组内容
            {
                L_arr[i - L] = arr[i];
            }

            for ( i = M; i <= R; i++)
            {
                R_arr[i - M] = arr[i];
            }
            i = 0; j = 0; k = L;
            while (i < left_size && j < right_size)
            {
                if (L_arr[i] < R_arr[j])
                {
                    arr[k++] = L_arr[i++];
                }

                else
                {
                    arr[k++] = R_arr[j++];
                }
            }

            while (i < left_size)
            {
                arr[k++] = L_arr[i++];
            }


            while (j < right_size)
            {
                arr[k++] = R_arr[j++];
            }
    
        }

      static  void merge_sort(int[]arr, int L, int R)
      {
        if(L == R)
        {
            return;
        }      
        else
        {
            int M = (L+R)/2;
            merge_sort(arr, L, M);
            merge_sort(arr, M+1, R);
            merge(arr, L, M+1, R);
        }
    }
    
    }