Create 1572-matrix-diagonal-sum.js

Author: chetannada

javascript/1572-matrix-diagonal-sum.js

@@ -0,0 +1,15 @@
+/**
+ * @param {number[][]} mat
+ * @return {number}
+ */
+var diagonalSum = function (mat) {
+    let sum = 0; // initialize sum to zero
+    let n = mat.length - 1; // initialize n to mat length - 1
+    for (let i = 0; i <= n; i++) { // loop through to 0 to n
+        sum += mat[i][i]; // add mat[i][i] to sum
+        if (i !== (n - i)) { // if i not equal to n - i then add mat[i][n - i] to sum
+            sum += mat[i][n - i];
+        }
+    }
+    return sum; // return sum;
+};