package school
import (
	"sort"
)
type School map[int][]string
type Grade struct {
	grade int
	name  []string
}
type Grades []Grade
func (g Grades) Len() int {
	return len(g)
}
func (g Grades) Less(i, j int) bool {
	return g[i].grade < g[j].grade
}
func (g Grades) Swap(i, j int) {
	g[i], g[j] = g[j], g[i]
	return
}
func New() *School {
	return &School{}
}
func (s *School) Add(student string, grade int) {
	(*s)[grade] = append((*s)[grade], student)
}
func (s *School) Grade(level int) []string {
	return (*s)[level]
}
func (s *School) Enrollment() []Grade {
	var ret Grades
	for k, v := range *s {
		sort.Strings(v)
		ret = append(ret, Grade{k, v})
	}
	sort.Sort(ret)
	return ret
}