Question

I was asked this question recently in an interview :

What is the most efficient way to find a repeated number in a sorted array?

My answer was based on using a hash table with key as array element and number of repetitions in array as value; iterate the array and update hash table. In the end, hash table can be checked for elements with count > 1 ; those are the repeated elements.

Is there a better way to do this ?

Thanks.

Answer 1

Well, you can do this with space of O(1). Since its a sorted array, all you need to do it to subtract the current number with the next one. If the result is 0 then you have a repeated number.