Sum of 'n' Numbers

Description:

Sum of 'n' Numbers

sum_of_n (or SequenceSum.sumOfN in Java) takes an integern and returns a List of length abs(n) + 1. The List 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]

My solution:

public class SequenceSum {public static int[] sumOfN(int n) {     int flag = n>0? 1:-1;    int[] result = new int[Math.abs(n)+1];    for(int i=0;i<Math.abs(n)+1;i++){        result[i] = i==0? 0:result[i-1]+i*flag;    }    return result;  }}

The best solution I think:

import java.util.stream.IntStream;public class SequenceSum {  public static int[] sumOfN(int n) {    int modifier = n < 0 ? -1 : 1;    int[] range = new int[Math.abs(n) + 1];    IntStream.rangeClosed(0, Math.abs(n)).forEach(      i -> {range[i] = i == 0 ? 0 : range[i - 1] + i * modifier;}    );    return range;  }}