diff --git a/cpp/2210/221021.cpp b/cpp/2210/221021.cpp
new file mode 100644
index 0000000..bfcb0ee
--- /dev/null
+++ b/cpp/2210/221021.cpp
@@ -0,0 +1,25 @@
+#include <vector>
+#include <unordered_set>
+
+/**
+ * 219. Contains Duplicate II
+ *
+ * Given an integer array nums and an integer k, return true if there are two distinct indices i and j in the array such that nums[i] == nums[j] and abs(i - j) <= k.
+ */
+
+class Solution {
+public:
+	static bool containsNearbyDuplicate(const std::vector<int>& nums, int k) {
+		int n = nums.size();
+		std::unordered_set<int> s(nums.begin(), nums.begin() + std::min(k, n));
+		if (s.size() != std::min(k, n))
+			return true;
+		for (int i = k; i < n; ++i) {
+			if (s.count(nums[i]))
+				return true;
+			s.insert(nums[i]);
+			s.erase(nums[i - k]);
+		}
+		return false;
+	}
+};
diff --git a/cpp/2210/CMakeLists.txt b/cpp/2210/CMakeLists.txt
index 9231094..b64967f 100644
--- a/cpp/2210/CMakeLists.txt
+++ b/cpp/2210/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2210)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2210 221021-CN.cpp)
+ADD_EXECUTABLE(2210 221021.cpp)