add: 230508

cpp/2305/LC230508.cpp

@@ -0,0 +1,21 @@
+#include <vector>
+
+/**
+ * 1572. Matrix Diagonal Sum
+ *
+ * Given a square matrix mat, return the sum of the matrix diagonals.
+ * Only include the sum of all the elements on the primary diagonal and all the elements on the secondary diagonal that are not part of the primary diagonal.
+ */
+
+class LC230508 {
+public:
+	static int diagonalSum(const std::vector<std::vector<int>>&) noexcept;
+};
+
+int LC230508::diagonalSum(const std::vector<std::vector<int>>& mat) noexcept {
+	const int n = mat.size();
+	int ret = 0;
+	for (int i = 0; i < n; ++i)
+		ret += mat[i][i] + mat[i][n - 1 - i];
+	return ret - (n & 1 ? mat[n >> 1][n >> 1] : 0);
+}

cpp/2305/defs.h

@@ -75,4 +75,9 @@ public:
 	static std::vector<int> longestObstacleCourseAtEachPosition(const std::vector<int>&) noexcept;
 };
 
+class LC230508 {
+public:
+	static int diagonalSum(const std::vector<std::vector<int>>&) noexcept;
+};
+
 #endif //LEETCODE_CPP_DEFS_H