题目
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.

答案

class Solution {
    public List<Integer> rightSideView(TreeNode root) {
        if(root == null) return new ArrayList<Integer>(); ;
        Queue<TreeNode> q = new LinkedList<TreeNode>();
        List<Integer> list = new ArrayList<Integer>();
        q.offer(root);
        while(q.size() != 0) {
            int curr_size = q.size();
            for(int i = 0; i < curr_size; i++) {
                TreeNode t = q.poll();
                if(i == curr_size - 1) list.add(t.val);
                if(t.left != null) q.offer(t.left);
                if(t.right != null) q.offer(t.right);                
            }
        }
        return list;
    }
}