package main

import (
	"fmt"
	"math/rand"
	"time"
)

func main() {
	// shuffle local
	hosts := []string{"a", "b", "c", "d", "e", "f"}
	shuffle(len(hosts), func(i, j int) {
		hosts[i], hosts[j] = hosts[j], hosts[i]
	})

	fmt.Println("shuffle string: ", hosts)

	ints := []int{1, 2, 3, 4, 5, 6}
	shuffle(len(ints), func(i, j int) {
		ints[i], ints[j] = ints[j], ints[i]
	})
	fmt.Println("shuffle int: ", ints)

	// shuffle new
	nhosts := []string{"a", "b", "c", "d", "e", "f"}
	new_nhosts := make([]string, len(nhosts))
	copy(new_nhosts, nhosts)
	shuffle(len(hosts), func(i, j int) {
		new_nhosts[i], new_nhosts[j] = new_nhosts[j], new_nhosts[i]
	})

	fmt.Println("origin : ", nhosts)
	fmt.Println("new : ", new_nhosts)
}

func shuffle(length int, exchange func(int, int)) {
	rand.Seed(int64(time.Now().Nanosecond()))
	for i := length - 1; i > 0; i-- {
		j := rand.Intn(i)
		exchange(i, j)
	}
}