199. Binary Tree Right Side View

class Solution {
    public List<Integer> rightSideView(TreeNode root) {
        List<Integer> res=new ArrayList<Integer>();
        rightView(root, res, 0);
        return res;
    }
    private void rightView(TreeNode node, List<Integer> res, int depth){
        if(node==null)
            return;
        if(depth==res.size())
            res.add(node.val);
        rightView(node.right, res, depth+1);
        rightView(node.left, res, depth+1);
    }
}

 

class Solution {
    public List<Integer> rightSideView(TreeNode root) {
        List<Integer> res=new ArrayList<Integer>();
        if(root==null)
            return res;
        Queue<TreeNode> que=new LinkedList<TreeNode>();
        que.add(root);
        que.add(null);
        boolean right=true;
        while(!que.isEmpty())
        {
            TreeNode node=que.poll();
            if(node==null)
            {
                right=true;
                if(!que.isEmpty())
                    que.add(node);
            }
            else
            {
                if(right==true)
                {
                    res.add(node.val);
                    right=false;
                }
                if(node.right!=null)que.add(node.right);
                if(node.left!=null)que.add(node.left);
            }
        }
        return res;
    }
}