Góc Lập Trình -191

class Solution {

 public class TreeNode {

  int val;

  TreeNode left;

  TreeNode right;

  TreeNode() {}

  TreeNode(int val) { this.val = val; }

  TreeNode(int val, TreeNode left, TreeNode right) {

   this.val = val;

   this.left = left;

  this.right = right;

  }

 }



 public List<Integer> rightSideView(TreeNode root) {

  if (root == null) {

   return new ArrayList<Integer>();

  }

  ArrayList<TreeNode> parents = new ArrayList();

  parents.add(root);



  ArrayList<Integer> rightside = new ArrayList();



  while (!parents.isEmpty()) {

   rightside.add(parents.get(parents.size() - 1).val);

   ArrayList<TreeNode> children = new ArrayList();



   for (TreeNode parent : parents) {

    if (parent.left != null) children.add(parent.left);

   if (parent.right != null) children.add(parent.right);

   }



   // prepare for next level

   parents = children;

  }

  return rightside;

 }

}