Binary Tree Right Side View

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 rightSideView(TreeNode root) {
        if(root == null) return new ArrayList(); ;
        Queue q = new LinkedList();
        List list = new ArrayList();
        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;
    }
}