Given the root
of a binary tree, imagine yourself standing on the right side
of it, return the values of the nodes you can see ordered from top to bottom.
Example 1:
Input: root = [1,2,3,null,5,null,4]
Output: [1,3,4]
Example 2:
Input: root = [1,null,3]
Output: [1,3]
Example 3:
Input: root = []
Output: []
Constraints:
[0, 100]
.100 <= Node.val <= 100
題目給了一個二元樹根結點 root
想要找到二元樹,每個level 最右邊的結點如下圖
直覺的作法是透過 Breadth First Traversal 廣度優先演算法實作
廣度優先演算法透過一個 queue ,每次把同一層的 node 照順序(由左而右)放到 queue 內
然後這時最右邊的結點就是我們要尋找的結點了