Array of size n, with one element n/2 times

Question

Given an array of n integers, where one element appears more than n/2 times. We need to find that element in linear time and constant extra space.

YAAQ: Yet another arra

Answer 1

This is what I thought initially.

I made an attempt to keep the invariant "one element appears more than n/2 times", while reducing the problem set.

Lets start comparing a[i], a[i+1]. If they're equal we compare a[i+i], a[i+2]. If not, we remove both a[i], a[i+1] from the array. We repeat this until i>=(current size)/2. At this point we'll have 'THE' element occupying the first (current size)/2 positions. This would maintain the invariant.

The only caveat is that we assume that the array is in a linked list [for it to give a O(n) complexity.]

What say folks?

-bhupi