Leetcode 199. right view of binary tree

BfS

class Solution {
    
    List<Integer>res=new LinkedList<>();
    public List<Integer> rightSideView(TreeNode root) {
    
        Queue<TreeNode>queue=new LinkedList<>();
        if(root==null) return res;
        queue.add(root);
        while(!queue.isEmpty()){
    
           int size=queue.size();
           
           for(int i=0;i<size;i++){
    
            TreeNode node=queue.poll();
            if(node.left!=null) queue.add(node.left);
            if(node.right!=null) queue.add(node.right);
            if(i==size-1) res.add(node.val);
           }
        }
        return res;
    }
}

DFS