diff --git a/contains-duplicate/DaleSeo.rs b/contains-duplicate/DaleSeo.rs
new file mode 100644
index 000000000..61a8717be
--- /dev/null
+++ b/contains-duplicate/DaleSeo.rs
@@ -0,0 +1,10 @@
+use std::collections::HashSet;
+
+// TC: O(n)
+// SC: O(n)
+impl Solution {
+    pub fn contains_duplicate(nums: Vec<i32>) -> bool {
+        let mut set = HashSet::new();
+        !nums.into_iter().all(|num| set.insert(num))
+    }
+}