Find a number where it appears exactly N/2 times

Question

Here is one of my interview question. Given an array of N elements and where an element appears exactly N/2 times and the rest N/2 elements are unique

Answer 1

I think you simply need to parse through the array keeping a backlog of two elements. As N/2 are equal and the rest is guaranteed to be distinct there must be one place i in your array where

a[i] == a[i-1] OR a[i] == a[i-2]

iterate once through your array and you have complexity of roughly 2*N which should be well inside O(N).

This answer is somewhat similar to the answer by Ganesh M and Dougie, but I think a little simpler.