diff --git a/contains-duplicate/sol.go b/contains-duplicate/sol.go
new file mode 100644
index 0000000..25e46de
--- /dev/null
+++ b/contains-duplicate/sol.go
@@ -0,0 +1,14 @@
+package main
+
+// Time: O(n)
+// Space: O(n)
+func containsDuplicate(nums []int) bool {
+	exists := make(map[int]bool)
+	for _, num := range nums {
+		if _, ok := exists[num]; ok {
+			return true
+		}
+		exists[num] = true
+	}
+	return false
+}