Question
Given 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.
For example:
Given the following binary tree,
1 <--- / \ 2 3 <--- \ \ 5 4 <---
You should return [1, 3, 4].
Credits:
Special thanks to @amrsaqr for adding this problem and creating all test cases.
Solution
This question basically is binary tree traversal. During the process, we keep a list and update the elements in it.
Code
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<Integer> rightSideView(TreeNode root) {
List<Integer> result = new ArrayList<Integer>();
traverse(result, root, 1);
return result;
}
void traverse(List<Integer> result, TreeNode node, int level) {
if (node == null) return;
if (level > result.size()) {
result.add(node.val);
}
traverse(result, node.right, level + 1);
traverse(result, node.left, level + 1);
}
}