feat: add string hamming distance algorithm (#747)

* feat: add string hamming distance algorithm

* refactor: use only a double quote for a single package import

---------

Co-authored-by: Rak Laptudirm <[email protected]>

Author: alirezaazadi

strings/hamming/hammingdistance.go

@@ -0,0 +1,31 @@
+/*
+This algorithm calculates the hamming distance between two equal length strings.
+The Hamming distance between two equal-length strings of symbols is the number of positions
+at which the corresponding symbols are different:
+https://en.wikipedia.org/wiki/Hamming_distance
+
+Note that we didn't consider strings as an array of bytes, therefore, we didn't use the XOR operator.
+In this case, we used a simple loop to compare each character of the strings, and if they are different,
+we increment the hamming distance by 1.
+
+Parameters: two strings to compare
+Output: distance between both strings */
+
+package hamming
+
+import "errors"
+
+func Distance(str1, str2 string) (int, error) {
+	if len(str1) != len(str2) {
+		return -1, errors.New("strings must have a same length")
+	}
+
+	hammingDistance := 0
+	for i := 0; i < len(str1); i++ {
+		if str1[i] != str2[i] {
+			hammingDistance++
+		}
+	}
+
+	return hammingDistance, nil
+}

strings/hamming/hammingdistance_test.go

@@ -0,0 +1,56 @@
+package hamming
+
+import "testing"
+
+var testCases = []struct {
+	name     string
+	string1  string
+	string2  string
+	expected int
+}{
+	{
+		"empty strings",
+		"",
+		"",
+		0,
+	},
+	{
+		"single character strings",
+		"A",
+		"A",
+		0,
+	},
+	{
+		"two different strings with a same length",
+		"TestString 1",
+		"TestString 2",
+		1,
+	},
+	{
+		"two different strings with a different length",
+		"TestString1",
+		"TestString",
+		-1,
+	},
+	{
+		"two same strings with a same length",
+		"TestString",
+		"TestString",
+		0,
+	},
+}
+
+func TestHammingDistance(t *testing.T) {
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			actual, err := Distance(tc.string1, tc.string2)
+			if err != nil {
+				if tc.expected != -1 {
+					t.Fatalf("Expected no error, but got %v", err)
+				}
+			} else if actual != tc.expected {
+				t.Errorf("Expected Hamming distance between strings: '%s' and '%s' is %v, but got: %v", tc.string1, tc.string2, tc.expected, actual)
+			}
+		})
+	}
+}