Given the root of a binary tree, display the values of its nodes while performing a level order traversal. Return the node values for all levels in a string separated by the character :. If the tree is empty, i.e., the number of nodes is $0$, then return “None” as the output.

Constraints:

• The number of nodes in the tree is in the range $[0, 500]$.

• $-10^3 \leq$ Node.data $\leq 10^3$

So far, you’ve probably brainstormed some approaches and have an idea of how to solve this problem. Let’s explore some of these approaches and figure out which one to follow based on considerations such as time complexity and any implementation constraints.

The naive approach would be to first calculate the height of the tree and then recursively traverse it, level by level. The printing function would be called for every level in the range $[1, height]$.

In the case of a skewed tree, the time complexity for this approach would be $O(n^2)$, where $n$ is the number of nodes. The space complexity is $O(n)$.