The right way to Clear up Easy Sq. Numbers in Golang

The problem

On this problem, you’ll be given a quantity n (n > 0) and your job can be to return the smallest sq. quantity N (N > 0) such that n + N can be an ideal sq.. If there is no such thing as a reply, return -1 (nil in Clojure, Nothing in Haskell, None in Rust).

resolve 13 = 36
<em>; as a result of 36 is the smallest excellent sq. that may be added to 13 to kind an ideal sq. => 13 + 36 = 49</em>

resolve 3 = 1 <em>; 3 + 1 = 4, an ideal sq.</em>
resolve 12 = 4 <em>; 12 + 4 = 16, an ideal sq.</em>
resolve 9 = 16 
resolve 4 = nil

The answer in Golang

Choice 1:

bundle answer
func Clear up(n int) int {
  res := -1
  for i:= 1; i * i < n; i++ {
    if n % i == 0 && (n / i - i) % 2 == 0 {
      res = (n / i - i) *  (n / i - i) / 4
    }
  }
  return res
}

Choice 2:

bundle answer
import "math"
func Clear up(n int) int {
  // n+a**2==b**2 => n=b2-a2=(a-b)(a+b) => b=(c+d)/2; a=d-b
  for i := int(math.Sqrt(float64(n))); i > 0; i-- {
    if npercenti == 0 {
      c, d := i, n/i
      b := (c + d) / 2
      a := d - b
      if a > 0 && n+a*a == b*b { return a * a }
    }
  }
  return -1
}

Choice 3:

bundle answer
import "math"
func Clear up(n int) int {
  upperBound := n
  lowerBound := 1
  for  lowerBound <= upperBound {
    sq. := lowerBound*lowerBound
    numToCheck := math.Sqrt(float64(sq. + n))
    if math.Ground(numToCheck) == math.Ceil(numToCheck) {
      return sq.
    }
    lowerBound++ 
  }
  return -1
}

Take a look at instances to validate our answer

bundle solution_test
import (
  . "github.com/onsi/ginkgo"
  . "github.com/onsi/gomega"
)
var _ = Describe("Instance exams", func() {
  It("It ought to work for fundamental exams", func() {
    Count on(Clear up(1)).To(Equal(-1))
    Count on(Clear up(2)).To(Equal(-1))
    Count on(Clear up(3)).To(Equal(1))
    Count on(Clear up(4)).To(Equal(-1))  
    Count on(Clear up(5)).To(Equal(4))
    Count on(Clear up(7)).To(Equal(9))
    Count on(Clear up(8)).To(Equal(1))
    Count on(Clear up(9)).To(Equal(16))
    Count on(Clear up(10)).To(Equal(-1))
    Count on(Clear up(11)).To(Equal(25))
    Count on(Clear up(13)).To(Equal(36))
    Count on(Clear up(17)).To(Equal(64))
    Count on(Clear up(88901)).To(Equal(5428900))
    Count on(Clear up(290101)).To(Equal(429235524)) 
  })
})