The challenge

Given a month as an integer from 1 to 12, return to which quarter of the year it belongs as an integer number.

For example: month 2 (February), is part of the first quarter; month 6 (June), is part of the second quarter; and month 11 (November), is part of the fourth quarter.

The solution in Golang

Option 1:

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package solution

func QuarterOf(month int) int {
  return (month + 2) / 3
}

Option 2:

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package solution

import("math")

func QuarterOf(month int) int {
  quarter := math.Ceil(float64(month)/3)
  return int(quarter)
}

Option 3:

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package solution

func QuarterOf(month int) int {
  q := [12]int{1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4}
  return q[month-1]
}

Test cases to validate our solution

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package our_test

import (
  "time"
  "math"
  "math/rand"

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

var _ = Describe("Test Example", func() {
  It("should test all values", func() {
    for i := 1; i < 13; i++ {
      Expect(QuarterOf(i)).To(Equal(solution(i)))
    }
  })
  It("should test random values", func() {
    rand.Seed(time.Now().UnixNano())
    for i := 1; i < 100; i++ {
      n := rand.Intn(12)+1
      Expect(QuarterOf(n)).To(Equal(solution(n)))
    }
  })
})

func solution(month int) int {
  return int(math.Ceil(float64(month) / 3))
}