Check if two string variables are anagram in Go (GoLang).

string-anagram.go

package strings

// AreAnagram returns whether string `s`
// is an anagram of string `t` (true) or not (false).
func AreAnagram(s string, t string) bool {
    if len(s) != len(t) {
        return false
    }
    set1, set2 := buildMultiSets(s, t)
    return  set1.isEqualTo(set2)
}

type multiSet struct {
    items map[byte]int
}

func newMultiSet() *multiSet {
    return &multiSet{
        items: make(map[byte]int),
    }
}

func buildMultiSets(str1, str2 string) (*multiSet, *multiSet) {
    if len(s1) != len(s2) {
        return nil, nil
    }
    set1, set2 := newMultiSet(), newMultiSet()
    for i := 0; i < len(str1); i++ {
        set1.add(str1[i])
        set2.add(str2[i])
    }
    return set1, set2
}

func (s *multiSet) add(b byte) {
    if s.has(b) {
        s.items[b]++
    } else {
        s.items[b] = 1
    }
}

func (s *multiSet) has(b byte) bool {
    _, ok := s.items[b]
    return ok
}

func (s *multiSet) countOf(b byte) int {
    c, ok := s.items[b]
    if !ok {
        return -1
    }
    return c
}

func (s *multiSet) isEqualTo(s2 *multiSet) bool {
    for b, c := range s.items {
        if c != s2.countOf(b) {
            return false
        }
    }
    return true
}