Software Engineering

# How to Calculate the Sum of the Numbers in the Nth row of a Triangle in Golang

## The challenge#

Given the triangle of consecutive odd numbers:

``````             1
3     5
7     9    11
13    15    17    19
21    23    25    27    29
...
``````

Calculate the sum of the numbers in the nth row of this triangle (starting at index 1) e.g.: (Input –> Output)

``````1 -->  1
2 --> 3 + 5 = 8
``````

## The solution in Golang#

Option 1:

``````package solution

func RowSumOddNumbers(n int) int {
return n * n * n
}
``````

Option 2:

``````package solution

import "math"

func RowSumOddNumbers(n int) int {
return int(math.Pow(float64(n), 3))
}
``````

Option 3:

``````package solution

func RowSumOddNumbers(n int) int {
res := 0
for i := (n - 1) * n + 1; i < n * (n + 1); i = i + 2 {
res = res + i
}
return res
}
``````

## Test cases to validate our solution#

``````package solution_test

import (
. "github.com/onsi/ginkgo"
. "github.com/onsi/gomega"
)

var _ = Describe("Fixed tests", func() {
It("Testing for 1", func() { Expect(RowSumOddNumbers(1)).To(Equal(1)) })
It("Testing for 2", func() { Expect(RowSumOddNumbers(2)).To(Equal(8)) })
It("Testing for 13", func() { Expect(RowSumOddNumbers(13)).To(Equal(2197)) })
It("Testing for 19", func() { Expect(RowSumOddNumbers(19)).To(Equal(6859)) })
It("Testing for 41", func() { Expect(RowSumOddNumbers(41)).To(Equal(68921)) })
It("Testing for 42", func() { Expect(RowSumOddNumbers(42)).To(Equal(74088)) })
It("Testing for 74", func() { Expect(RowSumOddNumbers(74)).To(Equal(405224)) })
It("Testing for 86", func() { Expect(RowSumOddNumbers(86)).To(Equal(636056)) })
It("Testing for 93", func() { Expect(RowSumOddNumbers(93)).To(Equal(804357)) })
It("Testing for 101", func() { Expect(RowSumOddNumbers(101)).To(Equal(1030301)) })
})
``````