Check if given binary tree is complete binary tree or not

A complete binary tree is a binary tree in which all levels except the last are completely filled, and all nodes in the last level are left-justified. In other words, a complete binary tree is a binary tree where every level is completely filled, except possibly the last level, and all nodes are as far left as possible.

To check if a given binary tree is a complete binary tree or not, we can follow the below steps:

1. Perform a level order traversal of the binary tree.
2. For each node encountered during the traversal, mark its left and right children as present and enqueue them.
3. If we encounter a null node, mark its left and right children as absent.
4. After the traversal, if we encounter a node whose left child is marked as absent, but the right child is present, or if we encounter a node whose left child is present, but the right child is absent or marked as absent, then the tree is not a complete binary tree.

If we do not encounter such a node during the traversal, then the given binary tree is a complete binary tree.

Code Example

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