199. 二叉树的右视图 --力扣 --JAVA

class Solution {
    List<Integer> ans = new ArrayList<>();
    public List<Integer> rightSideView(TreeNode root) {
        rightView(root,0);
        return ans;
    }
    public void rightView(TreeNode root, int height){
        if(root == null){
            return;
        }
        if(ans.size() <= height || ans.get(height) == null){
            ans.add(root.val);
        }
        height++;
        rightView(root.right, height);
        rightView(root.left, height);
    }
}