解题思路
利用双端队列进行广度优先遍历，将每一层的最后的节点加入结果集
代码
class Solution {
public List<Integer> rightSideView(TreeNode root) {
LinkedList<Integer> result = new LinkedList<>();
if (root == null) {
return result;
}
Deque<TreeNode> deque = new LinkedList<>();
deque.addLast(root);
while (!deque.isEmpty()) {
int size = deque.size();
result.add(deque.getLast().val);
for (int i = 0; i < size; i++) {
TreeNode head = deque.removeFirst();
if (head.left != null) {
deque.addLast(head.left);
}
if (head.right != null) {
deque.addLast(head.right);
}
}
}
return result;
}
}
