feat: solve No.1424

Author: BaffinLee

1401-1500/1424. Diagonal Traverse II.md

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+# 1424. Diagonal Traverse II
+
+- Difficulty: Medium.
+- Related Topics: Array, Sorting, Heap (Priority Queue).
+- Similar Questions: .
+
+## Problem
+
+Given a 2D integer array `nums`, return **all elements of **`nums`** in diagonal order as shown in the below images**.
+
+ 
+Example 1:
+
+![](https://assets.leetcode.com/uploads/2020/04/08/sample_1_1784.png)
+
+```
+Input: nums = [[1,2,3],[4,5,6],[7,8,9]]
+Output: [1,4,2,7,5,3,8,6,9]
+```
+
+Example 2:
+
+![](https://assets.leetcode.com/uploads/2020/04/08/sample_2_1784.png)
+
+```
+Input: nums = [[1,2,3,4,5],[6,7],[8],[9,10,11],[12,13,14,15,16]]
+Output: [1,6,2,8,7,3,9,4,12,10,5,13,11,14,15,16]
+```
+
+ 
+**Constraints:**
+
+
+	
+- `1 <= nums.length <= 105`
+	
+- `1 <= nums[i].length <= 105`
+	
+- `1 <= sum(nums[i].length) <= 105`
+	
+- `1 <= nums[i][j] <= 105`
+
+
+
+## Solution
+
+```javascript
+/**
+ * @param {number[][]} nums
+ * @return {number[]}
+ */
+var findDiagonalOrder = function(nums) {
+    var groups = [];
+    for (var i = nums.length - 1 ; i >= 0; i--) {
+        for (var j = 0; j < nums[i].length; j++) {
+            groups[i + j] = groups[i + j] || [];
+            groups[i + j].push(nums[i][j]);
+        }
+    }
+    return [].concat(...groups);
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(n).