add: 220215-CN

2202/220215.cpp

@@ -0,0 +1,27 @@
+#include <vector>
+#include <iostream>
+#include <unordered_set>
+
+/**
+ * 136. Single Number
+ * Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.
+ * You must implement a solution with a linear runtime complexity and use only constant extra space.
+ */
+
+class Solution {
+public:
+	static int singleNumber(const std::vector<int>& nums) {
+		std::unordered_set<int> s;
+		for (int i : nums)
+			if (s.count(i))
+				s.erase(i);
+			else
+				s.insert(i);
+		return *s.begin();
+	}
+};
+
+int main() {
+	std::cout << Solution::singleNumber({4,1,2,1,2});
+	return 0;
+}

2202/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2202)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2202 220215-CN.cpp)
+ADD_EXECUTABLE(2202 220215.cpp)