How to shuffle strings in arrays in golang?

Issue

So I created a program to help me decide which game to play. Before I start my problem let me show you my code:

package main

import (
    "fmt"
    "strconv"
    "time"
)

func main() {
    isArray := [10]string{"Paladins", "Overwatch", "CS:GO", "Tanki", "Left 4 Dead", "Rocket League", "Call Of Duty : AW", "Portal", "Star Citizen", "Star Wars : Battlefront"}
    fmt.Print("0,1,2,3,4,5,6,7,8,9 := ")

    var (
        va string
        ar string
    )

    fmt.Scanln(&va)
    i, _ := strconv.Atoi(va)

    fmt.Print("You Should Play : ")
    fmt.Print(isArray[i], "\n")
    fmt.Print("[Y/N] := ")
    fmt.Scanln(&ar)

    if ar != "N" || ar != "n" {
        fmt.Print("OK")
    }

    time.Sleep(3 * time.Second)
}

So the problems start when I already know which number would trigger a game, if I use it twice. So I am trying to make the strings random, like shuffling each time I use it, how can I do that?

Solution

Well, literally for your problem why not use rand.Intn() to choose a random number and print the game rather than make the user pick a number?

isArray := [10]string{"Paladins", "Overwatch", "CS:GO", "Tanki", "Left 4 Dead", "Rocket League", "Call Of Duty : AW", "Portal", "Star Citizen", "Star Wars : Battlefront"}
n := rand.Intn(9)
fmt.Printf("You Should Play : %s\n", isArray[n])

But if you want to shuffle strings in an array for the sake of it, then you can do it in place like this:

// Shuffle array in place
l := len(isArray)-1
for i := 0; i <=l; i++ {
    n := rand.Intn(l)
    // swap
    x := isArray[i]
    isArray[i] = isArray[n]
    isArray[n] = x
}

This should be O(n), though I’m not sure about the complexity of Intn. If you really want to be fancy, you could:

1. Create a second array (randomArray) of touples, containing a random number and element position in isArray.
2. Sort this array by the random number
3. Create a new array, copying elements of isArray, but ordered by our randomArray

Answered By – denis.lobanov

Answer Checked By – Marie Seifert (GoLangFix Admin)