Binary Tree Right Side View

Given a binary tree, imagine yourself standing on therightside 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].

Tips:

简单的BFS，需要注意要将一层中的所有点都加入queue而不是只加最右边的那个点。先右后左。

Code：

public class Solution {
    public List<Integer> rightSideView(TreeNode root) {
        List<Integer> res = new ArrayList<>();
        if (root == null) return res;
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            int size = queue.size();
            for (int i = 0; i < size; i++) {
                TreeNode curt = queue.poll();
                if (curt.right != null) queue.offer(curt.right);
                if (curt.left != null) queue.offer(curt.left);
                if (i == 0) res.add(curt.val);
            }
        }
        return res;
    }
}