Create 1572-matrix-diagonal-sum.kt

Author: a93a

kotlin/1572-matrix-diagonal-sum.kt

@@ -0,0 +1,15 @@
+class Solution {
+    fun diagonalSum(mat: Array<IntArray>): Int {
+        val n = mat.lastIndex
+
+        var sum = 0
+        for (i in 0..n) {
+            sum += mat[i][i] + mat[n - i][i]
+        }
+
+        if (n % 2 == 0)
+            sum -= mat[n/2][n/2]
+
+        return sum
+    }
+}