SequenceSum

SequenceSum

Sum of 'n' Numbers

sum_of_n (or SequenceSum.sumOfN in Java, SequenceSum.SumOfN in C#) takes an integer n and returns aList (an Array in Java/C#) of length abs(n) + 1. The List/Array contains the numbers in the arithmetic series produced by taking the sum of the consecutive integer numbers from 0 to n inclusive.

• n can also be 0 or a negative value.

Example:

5 -> [0, 1, 3, 6, 10, 15]

-5 -> [0, -1, -3, -6, -10, -15]

7 -> [0, 1, 3, 6, 10, 15, 21, 28]

Linq的无形装逼太过致命了

public class SequenceSum
{
   public static int[] SumOfN(int n)
        {
            //TODO: Write your solution here
return Enumerable.Range(0, Math.Abs(n) + 1).Select(item => Enumerable.Range(1, item).Aggregate(0, (x, y) => x + y)).Select(item => (n >= 0) ? item : -item).ToArray();
        }
}

 需要注意的是，Enumerable.Range中第一个参数是起始数字，第二个参数是序列总个数Enumerable.Range(5,4)  结果是5，6，7，8

其他人的解法：

using System.Linq;

public class SequenceSum
{
  public static int[] SumOfN(int n)
  {
    return Enumerable.Range(0, n + 1).Select(x => x * (x + 1) / 2).ToArray();
  }
}