func isAnagram(s string, t string) bool {
	occur := make([]int, 26)
	if len(s) != len(t) {
		return false
	}
	for i := range s {
		occur[int(s[i]-'a')]++
		occur[int(t[i]-'a')]--
	}
	for i := 0; i < 26; i++ {
		if occur[i] != 0 {
			return false
		}
	}
	return true
}