标题:199二叉树的右视图-中等
题目
示例1
输入: [1,2,3,null,5,null,4]
输出: [1,3,4]
示例2
输入: [1,null,3]
输出: [1,3]
示例3
输入: []
输出: []
提示
- 二叉树的节点个数的范围是
[0,100]
-100 <= Node.val <= 100
代码Java
public List<Integer> rightSideView(TreeNode root) {
List<Integer> ans = new ArrayList<>();
Deque<TreeNode> deque = new LinkedList<>();
if (root == null) return ans;
deque.add(root);
while (!deque.isEmpty()) {
int size = deque.size();
for (int i = 0; i < size; i++) {
TreeNode node = deque.pollFirst();
if (node.left != null) deque.add(node.left);
if (node.right != null) deque.add(node.right);
if (i == size - 1) {
ans.add(node.val);
}
}
}
return ans;
}