Add solution #1572

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,375 LeetCode solutions in JavaScript
+# 1,376 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1199,6 +1199,7 @@
 1567|[Maximum Length of Subarray With Positive Product](./solutions/1567-maximum-length-of-subarray-with-positive-product.js)|Medium|
 1568|[Minimum Number of Days to Disconnect Island](./solutions/1568-minimum-number-of-days-to-disconnect-island.js)|Hard|
 1569|[Number of Ways to Reorder Array to Get Same BST](./solutions/1569-number-of-ways-to-reorder-array-to-get-same-bst.js)|Hard|
+1572|[Matrix Diagonal Sum](./solutions/1572-matrix-diagonal-sum.js)|Easy|
 1576|[Replace All ?'s to Avoid Consecutive Repeating Characters](./solutions/1576-replace-all-s-to-avoid-consecutive-repeating-characters.js)|Medium|
 1598|[Crawler Log Folder](./solutions/1598-crawler-log-folder.js)|Easy|
 1657|[Determine if Two Strings Are Close](./solutions/1657-determine-if-two-strings-are-close.js)|Medium|

solutions/1572-matrix-diagonal-sum.js

@@ -0,0 +1,30 @@
+/**
+ * 1572. Matrix Diagonal Sum
+ * https://leetcode.com/problems/matrix-diagonal-sum/
+ * Difficulty: Easy
+ *
+ * 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.
+ */
+
+/**
+ * @param {number[][]} mat
+ * @return {number}
+ */
+var diagonalSum = function(mat) {
+  const n = mat.length;
+  let sum = 0;
+
+  for (let i = 0; i < n; i++) {
+    sum += mat[i][i];
+    sum += mat[i][n - 1 - i];
+  }
+
+  if (n % 2 === 1) {
+    sum -= mat[Math.floor(n / 2)][Math.floor(n / 2)];
+  }
+
+  return sum;
+};