Question Definition
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. For example: Given the following binary tree,
1 <---
/ \
2 3 <---
\ \
5 4 <---
You should return [1, 3, 4].
Java Solution
public List<Integer> rightSideView(TreeNode root) {
List<Integer> result = new LinkedList<>();
if(root == null) return result;
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(root);
queue.offer(null);
while(!queue.isEmpty()){
TreeNode cur = queue.poll();
if(cur == null){
if(queue.isEmpty()) break;
queue.offer(null);
cur = queue.poll();
}
if(queue.peek() == null) result.add(cur.val);
if(cur.left != null) queue.offer(cur.left);
if(cur.right != null) queue.offer(cur.right);
}
return result;
}
Comments