internal/da/da.go
func Build(keywords []string) (DoubleArray, error) {
	s := len(keywords)
	if s == 0 {
		return DoubleArray{}, nil
	}
	ids := make([]int, s, s)
	for i := range ids {
		ids[i] = i + 1
	}
	return BuildWithIDs(keywords, ids)
}
func Build(keywords []string) (DoubleArray, error) {
	s := len(keywords)
	if s == 0 {
		return DoubleArray{}, nil
	}
	ids := make([]int, s, s)
	for i := range ids {
		ids[i] = i + 1
	}
	return BuildWithIDs(keywords, ids)
}
// Build constructs a double array from given keywords.