Question

我有一个十元素的整数数组。我想按组对元素求和，所以例如我想在元素0处添加值，元素1的值，然后是元素2的值，然后是3，依此类推到元素9，然后添加元素1处的值，其值为2,3，直至9，直到每组2个值已加在一起并存储在变量中。然后，我想用3个组，4个组，5个组，一直到10个组重复该过程。每个结果总数存储在一个单独的变量中。到目前为止，我能弄清楚如何做到这一点的唯一方法是： -

int i = 0;
int p = 1;
int q = 2;
int r = 3;

while (i < NumArray.Length - 3)
{
    while (p < NumArray.Length - 2)
    {
        while (q < NumArray.Length-1)
        {
            while (r < NumArray.Length)
            {
                foursRet += NumArray[i] + NumArray[p] + NumArray[q]+ NumArray[r];
                r++; 
            }
            q++;
            r = q + 1;
        }
        p++;
        q = p + 1;
        r = q + 1;
    }
    i++;
    p = i + 1;
    q = i + 2;
    r = i + 3;
}

以上是4个组合的示例。我想知道是否有人能够向我展示一种不那么冗长，更优雅的方式来实现我想要的东西。非常感谢。

Answer 1

因为LINQ *的一切都更好：

using System; // Output is below
using System.Linq;
using System.Diagnostics;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var inputArray = Enumerable.Range(0, 10).ToArray();

            var grouped =
                from Buckets in Enumerable.Range(1, inputArray.Length)
                from IndexInBucket in Enumerable.Range(0, inputArray.Length / Buckets)
                let StartPosInOriginalArray = IndexInBucket * Buckets
                select new
                {
                    BucketSize = Buckets,
                    BucketIndex = StartPosInOriginalArray,
                    Sum = inputArray.Skip(StartPosInOriginalArray).Take(Buckets).Sum()
                };

            foreach (var group in grouped)
            {
                Debug.Print(group.ToString());
            }

            Console.ReadKey();
        }
    }
} // SCROLL FOR OUTPUT

{ BucketSize = 1, BucketIndex = 0, Sum = 1 }
{ BucketSize = 1, BucketIndex = 1, Sum = 2 }
{ BucketSize = 1, BucketIndex = 2, Sum = 3 }
{ BucketSize = 1, BucketIndex = 3, Sum = 4 }
{ BucketSize = 1, BucketIndex = 4, Sum = 5 }
{ BucketSize = 1, BucketIndex = 5, Sum = 6 }
{ BucketSize = 1, BucketIndex = 6, Sum = 7 }
{ BucketSize = 1, BucketIndex = 7, Sum = 8 }
{ BucketSize = 1, BucketIndex = 8, Sum = 9 }
{ BucketSize = 1, BucketIndex = 9, Sum = 10 }
{ BucketSize = 2, BucketIndex = 0, Sum = 3 }
{ BucketSize = 2, BucketIndex = 2, Sum = 7 }
{ BucketSize = 2, BucketIndex = 4, Sum = 11 }
{ BucketSize = 2, BucketIndex = 6, Sum = 15 }
{ BucketSize = 2, BucketIndex = 8, Sum = 19 }
{ BucketSize = 3, BucketIndex = 0, Sum = 6 }
{ BucketSize = 3, BucketIndex = 3, Sum = 15 }
{ BucketSize = 3, BucketIndex = 6, Sum = 24 }
{ BucketSize = 4, BucketIndex = 0, Sum = 10 }
{ BucketSize = 4, BucketIndex = 4, Sum = 26 }
{ BucketSize = 5, BucketIndex = 0, Sum = 15 }
{ BucketSize = 5, BucketIndex = 5, Sum = 40 }
{ BucketSize = 6, BucketIndex = 0, Sum = 21 }
{ BucketSize = 7, BucketIndex = 0, Sum = 28 }
{ BucketSize = 8, BucketIndex = 0, Sum = 36 }
{ BucketSize = 9, BucketIndex = 0, Sum = 45 }
{ BucketSize = 10, BucketIndex = 0, Sum = 55 }

^{* LINQ}

并非一切都好

Answer 2

如果我理解正确，你会得到一组长度为n的数字。您想从中选择m个数字的所有组合。然后，您想要对所有这些组合求和，最后计算这些总和的总和。

例如，给定n = 6个数字，您可以用15种不同的方式选择m = 4元素（数字是数字数组中的索引）：

如果n < 32（数组中不超过31个数字），您可以使用32位算术有效地生成索引。以下功能基于Gosper's hack：

IEnumerable<UInt32> GetIndexBits(Int32 m, Int32 n) {
  unchecked {
    var i = (UInt32) (1 << m) - 1;
    var max = (UInt32) (1 << n);;
    while (i < max) {
      yield return i;
      var u = (UInt32) (i & -i);
      var v = u + i;
      i = v + (((v ^ i)/u) >> 2);
    }
  }
}

使用m = 4和n = 6此函数将生成这些数字（以二进制形式显示）：

然后，您可以使用LINQ创建总和：

var m = 4;
var numbers = new[] { 1, 2, 3, 4, 5, 6 };
var sum = GetIndexBits(4, numbers.Length)
  .Select(
    bits => Enumerable
      .Range(0, numbers.Length)
      .Where(i => ((1 << i) & bits) != 0)
  )
  .Select(indices => indices.Sum(i => numbers[i]))
  .Sum();

使用提供的输入，总和将为210，这与foursRet包含数字1到6的问题中NumArray的结果相同。

添加数组的元素

2 个答案: