Right Side View of a Binary Tree

Problem Statement

Consider a binary tree. If you look at it from the right-hand side, return a list of values of the nodes that are visible from the top to the bottom.

Examples

Example 1:
Input: [10, 5, 15, null, 7, null, 20]
Output: [10, 15, 20]
Explanation:
      10        <---
     /  \
    5    15     <---
     \     \
      7     20  <---

Example 2:
Input: [3, 9, 8, 4, null, null, 7]
Output: [3, 8, 7]
Explanation:
      3         <---
     / \
    9   8       <---
   /     \
  4       7     <---

Constraints

• The number of nodes in the tree is between 0 and 1200.
• Node values range from -150 to 150.