diff --git a/cpp/2203/220318.cpp b/cpp/2203/220318.cpp
new file mode 100644
index 0000000..1dbfb28
--- /dev/null
+++ b/cpp/2203/220318.cpp
@@ -0,0 +1,30 @@
+#include <string>
+
+/**
+ * 316. Remove Duplicate Letters
+ * 1081. Smallest Subsequence of Distinct Characters
+ *
+ * Given a string s, remove duplicate letters so that every letter appears once and only once. You must make sure your result is the smallest in lexicographical order among all possible results.
+ */
+
+class Solution {
+public:
+	static std::string removeDuplicateLetters(const std::string& s) {
+		int lastViewed[26]{}, n = s.length();
+		for (int i = 0; i < n; ++i)
+			lastViewed[s[i] - 'a'] = i;
+		char ans[30]{};
+		bool used[26]{};
+		int top = -1;
+		for (int i = 0; i < n; ++i) {
+			if (!used[s[i] - 'a']) {
+				while (top >= 0 && ans[top] > s[i] && lastViewed[ans[top] - 'a'] > i) {
+					used[ans[top] - 'a'] = false;
+					ans[top--] = 0;
+				}
+				used[(ans[++top] = s[i]) - 'a'] = true;
+			}
+		}
+		return ans;
+	}
+};
diff --git a/cpp/2203/CMakeLists.txt b/cpp/2203/CMakeLists.txt
index 0630a05..18621ba 100644
--- a/cpp/2203/CMakeLists.txt
+++ b/cpp/2203/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2203)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2203 220317-CN.cpp)
+ADD_EXECUTABLE(2203 220318.cpp)