diff --git a/ch01/01_is_unique.go b/ch01/01_is_unique.go
index cee9c4a..5b915a3 100644
--- a/ch01/01_is_unique.go
+++ b/ch01/01_is_unique.go
@@ -1,5 +1,7 @@
 package ch01
 
+import "strings"
+
 // IsUnique determine if a string has all unique chars
 // This solution is based on HashTable (Go map) data structure
 func IsUnique(s string) bool {
@@ -30,3 +32,20 @@ func IsUniqueVanilla(s string) bool {
 
 	return true
 }
+
+// IsUniqueBits determines if a string has all unique chars (only works for ASCII)
+// This solution doesn't utilize any additional data structures and has O(n) time complexity
+func IsUniqueBits(s string) bool {
+
+	s = strings.ToLower(s)
+	var vector int32
+	for _, rune := range s {
+		index := rune - 'a'
+		mask := int32(1 << index)
+		if (vector & mask) == mask {
+			return false
+		}
+		vector = vector | mask
+	}
+	return true
+}
diff --git a/ch01/01_is_unique_test.go b/ch01/01_is_unique_test.go
index 5734dd0..d6a6185 100644
--- a/ch01/01_is_unique_test.go
+++ b/ch01/01_is_unique_test.go
@@ -21,3 +21,13 @@ func TestIsUniqueVanilla(t *testing.T) {
 		t.Error("'uniqke' is a unique string")
 	}
 }
+
+func TestIsUniqueBits(t *testing.T) {
+	if IsUniqueBits("unique") {
+		t.Error("'unique' is not a unique string")
+	}
+
+	if !IsUniqueBits("uniqke") {
+		t.Error("'uniqke' is a unique string")
+	}
+}
diff --git a/ch01/03_urlify.go b/ch01/03_urlify.go
index d9a8682..2e3b029 100644
--- a/ch01/03_urlify.go
+++ b/ch01/03_urlify.go
@@ -1,5 +1,7 @@
 package ch01
 
+import "regexp"
+
 // URLifyn returns the string with HTML encoded spacese
 // Expects real string length as a second parameter
 func URLifyn(s string, n int) string {
@@ -55,3 +57,11 @@ func URLify(s string) string {
 
 	return string(runes)
 }
+
+// UrlifyRegex returns the s string with HTML-encoded space characters.
+func UrlifyRegex(s string) string {
+
+	exp := regexp.MustCompile(" ")
+	return exp.ReplaceAllString(s, "%20")
+
+}
diff --git a/ch01/03_urlify_test.go b/ch01/03_urlify_test.go
index 4db9a15..0969f54 100644
--- a/ch01/03_urlify_test.go
+++ b/ch01/03_urlify_test.go
@@ -15,3 +15,10 @@ func TestUrlify(t *testing.T) {
 		t.Errorf("Expected \"%s\" after ULRification, got \"%s\"", expected, actual)
 	}
 }
+
+func TestUrlifyRegex(t *testing.T) {
+	actual, expected := UrlifyRegex("slug url"), "slug%20url"
+	if actual != expected {
+		t.Errorf("Expected \"%s\" after ULRification, got \"%s\"", expected, actual)
+	}
+}