What You See From the Right
A binary tree is given as a level-order array: tree[0] is the root, then the children of each real node are listed left to right, level by level. A missing child is written as null, and the children of a missing node are not listed at all. For example [1,2,3,null,4] is root 1 with children 2 and 3, where 2 has only a right child 4.
Imagine standing to the right of the tree and looking at it. On every level you only see the right-most node. Return the values you see, from the top level down.
Example 1
Input: tree = [1,2,3,null,5,null,4] Output: [1,3,4] Explanation: Levels are [1], [2,3], [5,4]; the right-most of each is 1, 3, 4.
Example 2
Input: tree = [1,null,3] Output: [1,3]
Constraints
- 0 <= number of nodes <= 10^4
- -100 <= node value <= 100
Hint 1
Process the tree level by level with a queue.
Hint 2
The last node of each level is the one visible from the right.
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