Why it is so important that a binary tree should be balanced?

Question

Given a binary tree print it in inward spiral order i.e first print level 1, then level n, then level 2, then n-1 and so on.

For Ex -

         1 
   2           3 
 4    5       6     7 
8 9  10 11  12 13  14 15 

Print- 1 15 14 13 12 11 10 9 8 2 3 7 6 5 4

Answer 1

Balanced binary tree insure that the search complexity O(logn) for all cases.
If tree is not balanced the worst case complexity can be O(n).