Combinations (77) from https://leetcode.com/problems/combinations/description/ ....too compex :-(

combinations.go

// Slice implements sort.Interface
type Slice []int

func (a Slice) Len() int           { return len(a) }
func (a Slice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a Slice) Less(i, j int) bool { return a[i] < a[j] }

func combine(n int, k int) [][]int {
	a := []int{}
	for i := 1; i <= n; i++ {
		a = append(a, i)
	}

	r := [][]int{}
	m := make(map[string]bool)
	r = append(r, a[:k])
	for i := k; i < n; i++ {
		// DEBUG
		// fmt.Printf("Array:%v, Add:%v\n", r, a[i])
		r = append(r, add(r, m, a[i], k)...)
	}
	return r
}

func add(results [][]int, m map[string]bool, v, k int) (out [][]int) {
	for _, vr := range results {
		// Explore each in index on the arrays from results
		for ia := range vr {
			// Do not reeplace values already replaced
			if vr[ia] > k {
				continue
			}
			// Create copy of array in results (don't want to modify it)
			s := append([]int{}, vr[:]...)
			s1 := Slice{}
			// Looks like I can't mix slice... and single values
			s1 = append(s1, s[:ia]...)
			s1 = append(s1, v)
			s1 = append(s1, s[ia+1:]...)
			// Sort elements to discard duplicates
			sort.Sort(s1)
			// Convert the array to an string to use as a key in a map
			ss := fmt.Sprintf("%v", s1)
			// Is this array in the map already?
			_, ok := m[ss]
			if !ok {
				out = append(out, s1)
				m[ss] = true
			}
			// DEBUG
			// fmt.Printf("New array:%v, Results:%v\n", s1, out)
		}
	}
	return out
}