# 107 Binary Tree Level Order Traversal II – Easy

### Problem:

Given a binary tree, return the bottom-up level order traversal of its nodes’ values. (ie, from left to right, level by level from leaf to root).

For example: Given binary tree {3,9,20,#,#,15,7},

```
3
```

/\
9 20 /\
15 7 return its bottom-up level order traversal as:

\[ \[15,7], \[9,20], \[3] ]

### Thoughts:

This is almost identical to version I. Only difference is the order of the level elements.

### Solutions:

```java
/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public List<List<Integer>> levelOrderBottom(TreeNode root) {
        Queue<TreeNode> qv = new LinkedList<TreeNode>();
        List<List<Integer>> result = new LinkedList<List<Integer>>();
        if (root == null) {
            return result;
        }
        qv.add(root);
        while (qv.size() > 0) {
            List<Integer> add = new LinkedList<Integer>();
            int n = qv.size();
            for (int i = 0; i < n; i ++) {
                TreeNode node = qv.remove();
                add.add(node.val);
                if (node.left !=null) {
                    qv.add(node.left);
                }
                if (node.right !=null) {
                    qv.add(node.right);
                }
            }
            result.add(0, add);
        }
        return result;
    }// level
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://ugopireddy.gitbook.io/leet-code-solutions/solutions_101_-_150/107_binary_tree_level_order_traversal_ii__easy.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.