How to make a go program recursive - arrays

Question

How could I make this go program recursive. I'm learning golang by writing a game number analyzer. I've been thinking and thinking on how to do this and can't come up with a working solution. Here is the link in the Google Playground. Any help would be greatly appreciated.
/*
File record.go
Author: Dan Huckson
Date: 20160120
Purpose: Number analyzer
*/
package main
import (
"fmt"
)
type Stats struct {
category map[string]Events
}
type Events struct {
event map[string]*Event
}
type Event struct {
value int64
}
func main() {
winners := [][]int{
{1, 2, 3, 4, 5, 6},
{2, 4, 6, 28, 26, 39},
{1, 4, 9, 10, 26, 39},
{1, 9, 19, 29, 26, 49},
{4, 5, 6, 28, 26, 49}}
keys := []string{"digits1", "digits2", "digits3", "digits4", "digits5", "digits6"}
stats := new(Stats)
stats.category = make(map[string]Events)
for _, key := range keys {
events, ok := stats.category[key]
if !ok {
events = *new(Events)
}
events.event = make(map[string]*Event)
stats.category[key] = events
}
fmt.Println()
for _, winner := range winners {
fmt.Println(winner)
stats.digits1("digits1", winner)
stats.digits2("digits2", winner)
stats.digits3("digits3", winner)
stats.digits4("digits4", winner)
stats.digits5("digits5", winner)
stats.digits6("digits6", winner)
}
}
func (stats *Stats) record(key string, balls string) {
event, ok := stats.category[key].event[balls]
if !ok {
event = new(Event)
stats.category[key].event[balls] = event
}
stats.category[key].event[balls].value += 1
word := ""
if len(balls) > 1 {
word = "Balls"
} else {
word = "Ball"
}
fmt.Printf("%s:%s\tCount:%d\n", word, balls_to_csv(balls), stats.category[key].event[balls].value)
}
func (stats *Stats) digits1(key string, winner []int) {
for i := 0; i < len(winner); i++ {
stats.record(key, string(winner[i]))
}
}
func (stats *Stats) digits2(key string, winner []int) {
for i := 0; i < len(winner)-1; i++ {
for j := i + 1; j < len(winner); j++ {
stats.record(key, string(winner[i])+string(winner[j]))
}
}
}
func (stats *Stats) digits3(key string, winner []int) {
for i := 0; i < len(winner)-2; i++ {
for j := i + 1; j < len(winner)-1; j++ {
for k := j + 1; k < len(winner); k++ {
stats.record(key, string(winner[i])+string(winner[j])+string(winner[k]))
}
}
}
}
func (stats *Stats) digits4(key string, winner []int) {
for i := 0; i < len(winner)-3; i++ {
for j := i + 1; j < len(winner)-2; j++ {
for k := j + 1; k < len(winner)-1; k++ {
for l := k + 1; l < len(winner); l++ {
stats.record(key, string(winner[i])+string(winner[j])+string(winner[k])+string(winner[l]))
}
}
}
}
}
func (stats *Stats) digits5(key string, winner []int) {
for i := 0; i < len(winner)-4; i++ {
for j := i + 1; j < len(winner)-3; j++ {
for k := j + 1; k < len(winner)-2; k++ {
for l := k + 1; l < len(winner)-1; l++ {
for m := l + 1; m < len(winner); m++ {
stats.record(key, string(winner[i])+string(winner[j])+string(winner[k])+string(winner[l])+string(winner[m]))
}
}
}
}
}
}
func (stats *Stats) digits6(key string, winner []int) {
for i := 0; i < len(winner)-5; i++ {
for j := i + 1; j < len(winner)-4; j++ {
for k := j + 1; k < len(winner)-3; k++ {
for l := k + 1; l < len(winner)-2; l++ {
for m := l + 1; m < len(winner)-1; m++ {
for n := m + 1; n < len(winner); n++ {
stats.record(key, string(winner[i])+string(winner[j])+string(winner[k])+string(winner[l])+string(winner[m])+string(winner[n]))
}
}
}
}
}
}
}
func balls_to_csv(key string) string {
s := ""
length := len(key)
for i := 0; i < length; i++ {
s += fmt.Sprintf("%d,", key[i])
}
return s[:len(s)-1]
}

Answer 1

As far as I can tell, you want to recursively find all the combinations of winning numbers. For example,
package main
import "fmt"
func combinations(n []int, c []int, ccc [][][]int) [][][]int {
if len(n) == 0 {
return ccc
}
if len(ccc) == 0 {
ccc = make([][][]int, len(n))
}
for i := range n {
cc := make([]int, len(c)+1)
copy(cc, c)
cc[len(cc)-1] = n[i]
ccc[len(cc)-1] = append(ccc[len(cc)-1], cc)
ccc = combinations(n[i+1:], cc, ccc)
}
return ccc
}
func main() {
n := []int{1, 2, 3, 4}
fmt.Println("winning numbers", n)
fmt.Println()
nw := 0
w := combinations(n, nil, nil)
fmt.Println("winning tickets:")
d := " digit : "
for i := range w {
fmt.Print(i+1, d)
d = " digits: "
for j := range w[i] {
nw++
fmt.Print(w[i][j], " ")
}
fmt.Println()
}
fmt.Println()
fmt.Println(nw, "winners")
}
Output:
winning numbers [1 2 3 4]
winning tickets:
1 digit : [1] [2] [3] [4]
2 digits: [1 2] [1 3] [1 4] [2 3] [2 4] [3 4]
3 digits: [1 2 3] [1 2 4] [1 3 4] [2 3 4]
4 digits: [1 2 3 4]
15 winners
Simplifying, you can see the recursion.
func combinations(n []int) {
if len(n) == 0 {
return
}
for i := range n {
combinations(n[i+1:])
}
return
}
The recursion terminates when len(n) == 0. In the for loop, i increases to len(n)-1, combinations(n[i+1:]) becomes combinations(n[len(n):]), and len(n[len(n):]) == 0, which will terminate the recursion.

Answer 2

Recursion is not a language specific concept. If you know what is recursion and if you know how to write a function in Go, then you can write a recursive function in Go.
This is a dummy recursive function in Go.
func f(n int) int {
if n < 0 {
return 0 // or something else
}
if n == 0 {
return 1
}
return n * f(n - 1)
}
This is a recursive function in Go, because,
It has a termination (base) condition(n <= 0)
f(n) depends on f(x) for all x < n.
It's written in Go.