gistfile1.go

// [[a b] [c d]] -> [[a c] [a d] [b c] [b d]]
func combinations(path []int, sets [][]int, acc *[][]int) {
	if len(sets) == 0 {
		*acc = append(*acc, path)
	} else {
		for _, el := range sets[0] {
			path := append(path, el)
			np := make([]int, len(path))
			copy(np, path)
			combinations(np, sets[1:], acc)
		}
	}
}