diff --git a/to-lower-case/DaleSeo.rs b/to-lower-case/DaleSeo.rs
new file mode 100644
index 0000000000..3fc2638784
--- /dev/null
+++ b/to-lower-case/DaleSeo.rs
@@ -0,0 +1,15 @@
+// TC: O(n)
+// SC: O(n)
+impl Solution {
+    pub fn to_lower_case(s: String) -> String {
+        s.chars()
+            .map(|c| {
+                if c.is_ascii_uppercase() {
+                    (c as u8 + (b'a' - b'A')) as char
+                } else {
+                    c
+                }
+            })
+            .collect()
+    }
+}