题目描述
方法思路
class Solution {
public List<List<Integer>> levelOrderBottom(TreeNode root) {
List<List<Integer>> res = new LinkedList<>();
if(root == null) return res;
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(root);
while(!queue.isEmpty()){
Queue<TreeNode> temp = new LinkedList<>();
List<Integer> list = new ArrayList<>();
while(!queue.isEmpty()){
TreeNode node = queue.poll();
list.add(node.val);
if(node.left != null)
temp.offer(node.left);
if(node.right != null)
temp.offer(node.right);
}
queue = temp;
res.add(0, list);
}
return res;
}
}