remove duplicate: hash map

main.go

func removeDuplicateMap(arr []int) []int {
	p := make(map[int]struct{})
	for _, v := range arr {
		p[v] = struct{}{}
	}
	r := make([]int, 0, len(p))
	for v := range p {
		r = append(r, v)
	}
	return r
}