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/**
* Definition for a binary tree node.
* 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;
* }
* }
*/
class Solution {
public List<List<Integer>> levelOrderBottom(TreeNode root) {
List<List<Integer>> list = new ArrayList<>();
Deque<TreeNode> queue = new ArrayDeque<>();
if(root==null)
return list;
queue.offerLast(root);
while(!queue.isEmpty())
{
ArrayList<Integer> l= new ArrayList<>();
int size=queue.size();
for(int i=0;i<size;i++)
{
TreeNode node=queue.pollFirst();
if(node.left!=null)
queue.offerLast(node.left);
if(node.right!=null)
queue.offerLast(node.right);
l.add(node.val);
}
list.add(l);
}
Collections.reverse(list);
return list;
}
}