Binary Tree Level Order Traversal
Given a binary tree (level-order array), return the level order traversal as each level on a separate line.
Output each level space-separated.
Example:
3,9,20,null,null,15,7
3 9 20 15 7
- The binary tree is constructed from the level-order array: the first element
3is the root, the next two elements9and20are its children, and the last two elements15and7are the children of20. - We start the level order traversal from the root
3, which is the first level and only contains the value3. - The next level consists of the root's children,
9and20, which are output as9 20. - The final level consists of the children of
20, which are15and7, output as15 7.
Constraints:
- 0 <= number of nodes <= 2000
Background Knowledge
The problem involves a binary tree, which is a data structure where each node has at most two children (i.e., left child and right child). In a binary tree, each level is fully filled before moving on to the next level, except for possibly the last level, which is filled from left to right. The level order traversal of a binary tree visits all the nodes at a given level before moving on to the next level. This type of traversal is also known as breadth-first traversal.
To understand the level order traversal, it's essential to know how a binary tree is represented. In this problem, the binary tree is given as a level-order array, where the nodes are arranged level by level, from left to right. For example, given a binary tree with the following structure:
1
/ \
2 3
/ \ \
4 5 6
The level-order array representation would be: [1, 2, 3, 4, 5, 6].
Background Knowledge: Key Concepts
Key concepts related to this problem include:
- Binary Tree: A tree-like data structure where each node has at most two children.
- Level Order Traversal: A traversal technique that visits all the nodes at a given level before moving on to the next level.
- Breadth-First Traversal: Another name for level order traversal, which visits all the nodes at a given level before moving on to the next level.
- Queue Data Structure: A data structure that follows the First-In-First-Out (FIFO) principle, which is often used to implement level order traversal.
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