Add solution #498

Author: JoshCrozier

README.md

@@ -399,6 +399,7 @@
 495|[Teemo Attacking](./0495-teemo-attacking.js)|Easy|
 496|[Next Greater Element I](./0496-next-greater-element-i.js)|Easy|
 497|[Random Point in Non-overlapping Rectangles](./0497-random-point-in-non-overlapping-rectangles.js)|Medium|
+498|[Diagonal Traverse](./0498-diagonal-traverse.js)|Medium|
 500|[Keyboard Row](./0500-keyboard-row.js)|Easy|
 501|[Find Mode in Binary Search Tree](./0501-find-mode-in-binary-search-tree.js)|Easy|
 502|[IPO](./0502-ipo.js)|Hard|

solutions/0498-diagonal-traverse.js

@@ -0,0 +1,45 @@
+/**
+ * 498. Diagonal Traverse
+ * https://leetcode.com/problems/diagonal-traverse/
+ * Difficulty: Medium
+ *
+ * Given an m x n matrix mat, return an array of all the elements of the array in a diagonal order.
+ */
+
+/**
+ * @param {number[][]} mat
+ * @return {number[]}
+ */
+var findDiagonalOrder = function(mat) {
+  const result = new Array(mat.length * mat[0].length);
+
+  for (let r = 0, c = 0, d = 1, i = 0; i < mat.length * mat[0].length;) {
+    result[i++] = mat[r][c];
+
+    if (d === 1) {
+      if (c === mat[0].length - 1) {
+        r++;
+        d = -1;
+      } else if (r === 0) {
+        c++;
+        d = -1;
+      } else {
+        r--;
+        c++;
+      }
+    } else {
+      if (r === mat.length - 1) {
+        c++;
+        d = 1;
+      } else if (c === 0) {
+        r++;
+        d = 1;
+      } else {
+        r++;
+        c--;
+      }
+    }
+  }
+
+  return result;
+};