add step3 for Valid Anagram

Author: rihib

pullrequests/valid_anagram/step3.go

@@ -0,0 +1,32 @@
+//lint:file-ignore U1000 Ignore all unused code
+package validanagram
+
+func isAnagram_step3(s string, t string) bool {
+	return frequency(s) == frequency(t)
+}
+
+func frequency(s string) [26]int {
+	var f [26]int
+	for _, r := range s {
+		f[r-'a']++
+	}
+	return f
+}
+
+// ちゃんとUnicodeに対応させるなら結合文字などを考慮する必要がある
+// https://github.com/rihib/leetcode/pull/5#discussion_r1706198268
+func isAnagram_unicode_step3(s string, t string) bool {
+	frequency := make(map[rune]int)
+	for _, r := range s {
+		frequency[r]++
+	}
+	for _, r := range t {
+		frequency[r]--
+	}
+	for _, n := range frequency {
+		if n != 0 {
+			return false
+		}
+	}
+	return true
+}