give root complete binary tree return number node treeaccorde Wikipedia level possibly completely fill complete binary tree node level far leave possible it 1 2h node inclusive level hDesign algorithm run on time complexity Example 1input root 123456output 6Example 2input root Output 0example 3input root 1output 1 ConstraintsThe number nod tree range 0 5 1040 Nodeval 5 104the tree guarantee complete