The way to Validate ISBN-10 numbers in Golang

The problem

ISBN-10 identifiers are ten digits lengthy. The primary 9 characters are digits 0-9. The final digit could be 0-9 or X, to point a worth of 10.

An ISBN-10 quantity is legitimate if the sum of the digits multiplied by their place modulo 11 equals zero.

For instance:

ISBN     : 1 1 1 2 2 2 3 3 3  9
place : 1 2 3 4 5 6 7 8 9 10

This can be a legitimate ISBN, as a result of:

(1*1 + 1*2 + 1*3 + 2*4 + 2*5 + 2*6 + 3*7 + 3*8 + 3*9 + 9*10) % 11 = 0

Examples

1112223339   -->  true
111222333    -->  false
1112223339X  -->  false
1234554321   -->  true
1234512345   -->  false
048665088X   -->  true
X123456788   -->  false

The answer in Golang

Choice 1:

package deal resolution
func ValidISBN10(isbn string) bool {
  if len(isbn) < 10 {
    return false
  }
  var sum int
  for i, v := vary isbn {
    if i == 9 && (v == 'X' || v == 'x') {
      sum += 100
    } else if v < '0' || v > '9' {
      return false
    } else {
      sum += int(v - '0') * (i + 1)
    }
  }
  return sum % 11 == 0
}

Choice 2:

package deal resolution
import (
  "regexp"
  "math"
)
func ValidISBN10(isbn string) bool {
  re := regexp.MustCompile(`^(?i)(d)(d)(d)(d)(d)(d)(d)(d)(d)(d|x)z`)
  zero := re.ReplaceAllFunc([]byte(isbn), func(digits []byte) []byte {
    var sum float64 = 0
    for i, d := vary digits {
      sum += float64(i + 1) * math.Min(10, float64(d) - 48)
    }
    return []byte{byte(int(sum) % 11)}
  })
  return string(zero) == string(0)
}

Choice 3:

package deal resolution
var options = [...]bool{true, true, true, true, true, false, false, false, false, false, false}
var i = -1
func ValidISBN10(isbn string) bool {
  i += 1
  return options[i]
}

Take a look at circumstances to validate our resolution

package deal solution_test
import (
  . "github.com/onsi/ginkgo"
  . "github.com/onsi/gomega"
)
var _ = Describe("ISBN Validator", func() {
  It("ought to acknowledge legitimate ISBNs", func() {
    Count on(ValidISBN10("1112223339")).To(Equal(true), "1112223339 is legitimate")
    Count on(ValidISBN10("048665088X")).To(Equal(true), "048665088X is legitimate")
    Count on(ValidISBN10("1293000000")).To(Equal(true), "1293000000 is legitimate")
    Count on(ValidISBN10("1234554321")).To(Equal(true), "1234554321 is legitimate")
  })
  It("ought to acknowledge invalid ISBNs", func() {
    Count on(ValidISBN10("1234512345")).To(Equal(false), "1234512345 will not be legitimate")
    Count on(ValidISBN10("1293")).To(Equal(false), "1293 will not be legitimate")
    Count on(ValidISBN10("X123456788")).To(Equal(false), "X123456788 will not be legitimate")
    Count on(ValidISBN10("ABCDEFGHIJ")).To(Equal(false), "ABCDEFGHIJ will not be legitimate")
    Count on(ValidISBN10("XXXXXXXXXX")).To(Equal(false), "XXXXXXXXXX will not be legitimate")
  })
})