Interview Question

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You can do this in linear time. Obtain the in-order traversal of both trees -- these are sorted sequences. Then, merge the two sequences (the same way the merge step of mergesort works). Since the resulting sequence will itself be sorted, all the duplicates can then be easily removed because they will be adjacent to each other.

I use the term "sequence" because the exact implementation can vary. You can use arrays or linked lists to hold the intermediate sequences. You can also avoid the use of intermediate structures altogether -- just traverse the trees and keep track of where you are in the traversal (that's what using an iterator does). Then merge as you go, and don't output an element to the output if the previous element placed there is equal to the current one.

- eugene.yarovoi January 31, 2015 | Flag Reply

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