English
199. Binary Tree Right Side View 
Problem Statement:
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:
- The number of nodes in the tree is in the range [0, 100].
- -100 <= Node.val <= 100
Solution:
java
public class BinaryTreeRightSideView {
int maxLevel = 0;
List<Integer> arr = new ArrayList<Integer>();
public List<Integer> rightSideView(TreeNode root) {
rightSideView(root, 1);
return arr;
}
private void rightSideView(TreeNode root, int level) {
if (root == null)
return;
if (maxLevel < level) {
arr.add(root.val);
maxLevel = level;
}
rightSideView(root.right, level + 1);
rightSideView(root.left, level + 1);
}
}
...