All the Ways to Divide an Array in Two in Golang

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a = ["az", "toto", "picaro", "zone", "kiwi"] -->
[("az", "toto picaro zone kiwi"), ("az toto", "picaro zone kiwi"), ("az toto picaro", "zone kiwi"), ("az toto picaro zone", "kiwi")]

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package solution
import ("strings"; "fmt")
func PartList(l []string) (r string) {
  for i := 1; i < len(l); i++ {
    a := strings.Join(l[0:i], " ")
    b := strings.Join(l[i:], " ")
    r += fmt.Sprintf("(%s, %s)", a, b)
  }
  return
}

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package solution
import . "strings"
func PartList(arr []string) string {
  var sb Builder
  n := len(arr)
  for x := 1; x < n; x++ {
    sb.WriteString("(" + Join(arr[:x], " ") + ", " + Join(arr[x:], " ") + ")")
  }
  return sb.String()
}

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package solution
import (
"fmt"
"strings"
)
func PartList(arr []string) string {
  str := ""
  for i := 0 ; i < len(arr) - 1 ; i++ {
    str += appended(arr, i)
  }
  fmt.Println(str)
  return str
}
func appended(strs []string, index int) string {
  tmp := make([]string, len(strs))
  copy(tmp, strs)
  tmp[index] += ","
  return fmt.Sprintf("(%s)", strings.Join(tmp, " "))
}

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package solution_test
import (
  . "github.com/onsi/ginkgo"
  . "github.com/onsi/gomega"
  "strings"
  "math/rand"
  "time"
)

func dotest(arr []string, exp string) {
    var ans = PartList(arr)
    Expect(ans).To(Equal(exp))
}

func randStringBytes(n int) string {
    const letterBytes = "abcde1fghij2klmno3pqrs4tuvwxyz5ABCDEF6GHIJKL7MNOPQR8STUV9WXYZ"
    b := make([]byte, n)
    for i := range b {
        b[i] = letterBytes[rand.Intn(len(letterBytes))]
    }
    return string(b)
}
func random(min, max int) int {
    return rand.Intn(max - min) + min
}
func doStringArray(n int) []string {
    var res []string
    for i := 0; i < n; i++ {
        res = append(res, randStringBytes(random(5, 15)))
    }
    return res
}
func PartListPVX(arr []string) string {
    res := ""
    for i := 1; i <= len(arr) - 1; i++ {
        res += "(" + strings.Join(arr[0:i], " ") + ", " + strings.Join(arr[i:len(arr)], " ") + ")"
    }
    return res
}

func randomtest() {
    rand.Seed(time.Now().UTC().UnixNano())
    for i := 0; i < 100; i++ {
        k := random(8, 12) 
        s := doStringArray(k)
        sol := PartListPVX(s)
        dotest(s, sol)
    }
}

var _ = Describe("Tests PartList", func() {

    It("should handle basic cases", func() {
        dotest([]string{"I", "wish", "I", "hadn't", "come"},
            "(I, wish I hadn't come)(I wish, I hadn't come)(I wish I, hadn't come)(I wish I hadn't, come)")
        dotest([]string{"cdIw", "tzIy", "xDu", "rThG"}, 
            "(cdIw, tzIy xDu rThG)(cdIw tzIy, xDu rThG)(cdIw tzIy xDu, rThG)")
        dotest([]string{"vJQ", "anj", "mQDq", "sOZ"}, 
            "(vJQ, anj mQDq sOZ)(vJQ anj, mQDq sOZ)(vJQ anj mQDq, sOZ)")
        dotest([]string{"mkC", "WoiP", "pCHh", "mkv"}, "(mkC, WoiP pCHh mkv)(mkC WoiP, pCHh mkv)(mkC WoiP pCHh, mkv)")
        dotest([]string{"vHW", "bPq", "pme", "jJr", "HGHV"}, 
            "(vHW, bPq pme jJr HGHV)(vHW bPq, pme jJr HGHV)(vHW bPq pme, jJr HGHV)(vHW bPq pme jJr, HGHV)")
        dotest([]string{"YZd", "ptUD", "IXr"}, "(YZd, ptUD IXr)(YZd ptUD, IXr)")

        dotest([]string{"dOXj", "nMlK", "QGT", "LSt", "BHNR"}, 
            "(dOXj, nMlK QGT LSt BHNR)(dOXj nMlK, QGT LSt BHNR)(dOXj nMlK QGT, LSt BHNR)(dOXj nMlK QGT LSt, BHNR)")
    })
    It("should handle random cases", func() {
        randomtest()
    })
})