Construct a complete binary tree from given array in level order fashion

Given an array of elements, our task is to construct a complete binary tree from this array in a level order fashion. That is, elements from the left in the array will be filled in the tree level-wise starting from level 0.

Examples: 
 

Input  :  arr[] = {1, 2, 3, 4, 5, 6}
Output : Root of the following tree
                 1
                / \
               2   3
              / \ /
             4  5 6

Construct a complete binary tree from given array in level order fashion : https://www.geeksforgeeks.org/construct-complete-binary-tree-given-array/