public class Solution {
    public static int dominator(int[] a) {
        int size = 0;
        int value = 0;
        int index = 0;

        for (int k = 0; k < a.length; k++) {
            int v = a[k];
            if (size == 0) {
                size++;
                value = v;
                index = k;
            } else if (value != v) {
                size--;
            } else {
                size++;
            }
        }
        int candidate = size > 0 ? value : -1;

        int count = 0;
        for (int v : a) {
            if (v == candidate) {
                count++;
            }
        }
        if (count <= a.length / 2.0) {
            index = -1;
        }

        return index;
    }
}