Create 1572-matrix-diagonal-sum.java

Author: Tetsuya3850

java/1572-matrix-diagonal-sum.java

@@ -0,0 +1,13 @@
+class Solution {
+    public int diagonalSum(int[][] mat) {
+        int res = 0;
+        int n = mat.length;
+
+        for (int i = 0; i < n; i++) {
+            res += mat[i][i];
+            res += mat[i][n - 1 - i];
+        }
+
+        return res - (n % 2 == 1 ? mat[n / 2][n / 2] : 0);
+    }
+}