alphabet.go
func dedupe(s []string) []string {
	var out []string
	m := make(map[string]bool)

	for _, char := range s {
		if _, ok := m[char]; !ok {
			m[char] = true
			out = append(out, char)
		}
	}

	return out
}
func dedupe(s []string) []string {
	var out []string
	m := make(map[string]bool)

	for _, char := range s {
		if _, ok := m[char]; !ok {
			m[char] = true
			out = append(out, char)
		}
	}

	return out
}
// dudupe removes duplicate characters from s.