Build balanced tree from an array

#1

What is the meaning of this line -
“THE HEIGHT OF THE BALANCE TREE SHOULD BE O(LOGN)”
,Yeh smjh ni aaya ?

#2

See a balance tree will be a complete binary tree, if difference between left and right heights is not more than 1 then tree is height balanced tree, right?
So now notice this,

at level 0 - 1 nodes
at level 1 - 2 nodes
at level 2 - 4 nodes
at level 3 - 8 nodes
at level 4 - 16 nodes
        ()
      /    \
     ()     ()
    /  \    /  \
  ()    () ()   ()
 / \
()  ()

By noticing this you will see a log graph so that’s why we that if there are total n nodes in a binary tree then it’s height will be O(log N)

#3

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