Dominator

        /// <summary>
        /// Solution
        /// 100/100
        /// </summary>
        /// <param name="A"></param>
        /// <returns></returns>
        public static int solution(int[] A)
        {
            int maxKey;
            int maxValue;

            if (A.Length == 0)
                return -1;
            if (A.Length == 1)
                return 0;

            Dictionary<int, int> dic = new Dictionary<int, int>();
            foreach (int num in A)
            {
                if (!dic.ContainsKey(num))
                    dic.Add(num, 1);
                else
                    dic[num]++;
            }

            dic = dic.OrderBy(o => o.Value).ToDictionary(o => o.Key, p => p.Value);
            maxKey = dic.Keys.Last<int>();
            maxValue = dic.Values.Last<int>();

            if (maxValue > A.Length / 2)
            {
                for (int i = 0; i < A.Length; i++)
                    if (A[i] == maxKey)
                        return i;
            }

            return -1;
        }