Selections Permutation

selections.go

package main

import (
	"bytes"
	"fmt"
	"strconv"
)

func selectionHelper(runners string, chosen string) {
	if runners == "" {
		fmt.Println(chosen)
		return
	}

	for index := 0; index < len(runners); index++ {

		char := runners[index : index+1]
		chosen = chosen + char
		runners = runners[0:index] + runners[index+1:]

		selectionHelper(runners, chosen)

		runners = runners[0:index] + char + runners[index:]
		chosen = chosen[:len(chosen)-1]
	}

}

func insert(s []int, at int, val int) []int {
	// Make sure there is enough room
	s = append(s, 0)
	// Move all elements of s up one slot
	copy(s[at+1:], s[at:])
	// Insert the new element at the now free position
	s[at] = val
	return s
}

func getAllCombinations(runners []int, combinations int, chosen []int, result chan<- []int) {
	for index, runner := range runners {
		if combinations > 1 {
			crunners := make([]int, len(runners))
			copy(crunners, runners)
			getAllCombinations(
				append(crunners[:index], crunners[index+1:]...),
				combinations-1,
				append(chosen, runner),
				result,
			)
		} else {
			result <- append(chosen, runner)
		}
	}

}

//GetSelections get selections for a given runner count
func GetSelections(count int) {

	var runners, chosen []int
	var buff bytes.Buffer
	for r := 1; r <= 4; r++ {
		runners = append(runners, r)
		buff.WriteString(strconv.Itoa(r))
	}

	result := make(chan []int)
	go func() {
		defer close(result)
		defer fmt.Println("closing channel")
		getAllCombinations(runners, 3, chosen, result)
	}()

	for result := range result {
		fmt.Println(result)
	}

	// selectionHelper(buff.String(), "")

}