Strutil: HammingDistance func (#197)

* Strutil: HammingDistance func

The Hamming distance is the number of positions at which the corresponding symbols are different

* Add hamming distance doc

strutil/string.go

@@ -4,6 +4,7 @@
 package strutil
 
 import (
+	"errors"
 	"regexp"
 	"strings"
 	"unicode"
@@ -594,3 +595,24 @@ func SubInBetween(str string, start string, end string) string {
 
 	return ""
 }
+
+// HammingDistance calculates the Hamming distance between two strings.
+// The Hamming distance is the number of positions at which the corresponding symbols are different.
+// This func returns an error if the input strings are of unequal lengths.
+func HammingDistance(a, b string) (int, error) {
+	if len(a) != len(b) {
+		return -1, errors.New("a length and b length are unequal")
+	}
+
+	ar := []rune(a)
+	br := []rune(b)
+
+	var distance int
+	for i, codepoint := range ar {
+		if codepoint != br[i] {
+			distance++
+		}
+	}
+
+	return distance, nil
+}