Programming Test - Codility - Dominator [closed]

Answer 1

This question looks hard if a small trick does not come to the mind :). I found this trick in this document of codility : https://codility.com/media/train/6-Leader.pdf.

The linear solution is explained at the bottom of this document.

I implemented the following java program which gave me a score of 100 on the same lines.

public int solution(int[] A) {

    Stack stack = new Stack();

    for (int i =0; i < A.length; i++)
    {
        if (stack.empty())
            stack.push(new Integer(A[i]));
        else
        {
            int topElem = stack.peek().intValue();
            if (topElem == A[i])
            {
                stack.push(new Integer(A[i]));
            }
            else
            {
                stack.pop();
            }
        }            
    }

    if (stack.empty())
        return -1;

    int elem = stack.peek().intValue();
    int count = 0;
    int index = 0;
    for (int i = 0; i < A.length; i++)
    {
        if (elem == A[i])
        {
            count++;
            index = i;
        }
    }

    if (count > ((double)A.length/2.0))
        return index;
    else
        return -1;
}