# DIY: Binary Tree Level Order Traversal

Solve the interview question "Binary Tree Level Order Traversal" yourself in this lesson.

We'll cover the following

## Problem statement

Given a binary tree, populate an array to represent its level-by-level traversal. You should populate the values of each levels’ nodes from left to right in separate subarrays.

### Input

The input will be a binary tree, and you will be provided with its root node. The following is an example input:

    3
/ \
9  20
/  \
15   7


### Output

The output will be an array of arrays in which each nested array will represent the elements of a single level. For the above input, the output will be:

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


## Coding exercise

For this coding exercise, you need to implement the function traverse(root), where root is the root node of the binary tree. The function should return the level-by-level values of the binary tree in separate subarrays.

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