add: 230331-CN

cpp/2303/230331-CN.cpp

@@ -0,0 +1,24 @@
+#include <unordered_set>
+#include <vector>
+#include <algorithm>
+
+/**
+ * 2367. Number of Arithmetic Triplets
+ *
+ * You are given a 0-indexed, strictly increasing integer array nums and a positive integer diff. A triplet (i, j, k) is an arithmetic triplet if the following conditions are met:
+ *
+ * i < j < k,
+ * nums[j] - nums[i] == diff, and
+ * nums[k] - nums[j] == diff.
+ * Return the number of unique arithmetic triplets.
+ */
+
+class Solution {
+public:
+	static int arithmeticTriplets(const std::vector<int>& nums, int diff) {
+		std::unordered_set<int> s(nums.begin(), nums.end());
+		return std::count_if(nums.begin(), nums.end(), [&](int x) {
+			return s.count(x + diff) && s.count(x + 2 * diff);
+		});
+	}
+};

cpp/2303/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2303)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2303 230330-CN.cpp)
+ADD_EXECUTABLE(2303 230331-CN.cpp)