Given a Binary Tree, check whether the given Binary Tree is Complete Binary Tree or not. A complete binary tree is a binary tree in which every level, except possibly the last, is completely filled, and all nodes should be as much close to left as possible.
Examples:
Input: root = [1, 2, 3]
Output: true
Explanation: The given tree is complete binary tree.
Input: root = [1, 2, 3, 4, N, 5, 6]
Output: false
Explanation: The given tree is not complete binary tree because in last level all nodes are not at left.
Constraints:
1<=number of node<=105
0 <= node -> data <= 106
