Question

Two balanced binary trees are given with m and n elements respectively. They can be merged into a balanced binary search tree in ____ time.

(a) O(m+n)

(b) O(mn)

(c) O(m)

(d) O(mlog n)

My question is taken from Binary Trees topic in chapter Binary Trees of Data Structures & Algorithms I

The question was posed to me in a job interview.

Answer 1

Correct option is (a) O(m+n)

To explain: First we store the in-order traversals of both the trees in two separate arrays and then we can merge these sorted sequences in O(m+n) time. And then we construct the balanced tree from this final sorted array.