Ranking.cs

static int[] GetRanks_Sort(int[] input)
        {
            int[] sorted = new int[input.Length];
            Array.Copy(input, sorted, input.Length);
            Array.Sort(sorted);

            var ranked = new Dictionary<int, int>();
            int rank = 1;
            int number = sorted[0];
            ranked.Add(sorted[0], rank);
            for (int i = 1; i < sorted.Length; i++)
            {
                if (sorted[i] != number)
                {
                    number = sorted[i];
                    ranked.Add(number, i + 1);
                }
            }

            int[] result = new int[input.Length];
            for (int i = 0; i < input.Length; i++)
            {
                result[i] = ranked[input[i]];
            }
            return result;
        }

        static int[] GetRanks_Hash(int[] input)
        {
            var frequencies = new Dictionary<int, int>();
            for (int i = 0; i < input.Length; i++)
            {
                if (frequencies.ContainsKey(input[i]))
                {
                    frequencies[input[i]]++;
                }
                else
                {
                    frequencies.Add(input[i], 1);
                }
            }

            int[] sorted = new int[frequencies.Count];
            frequencies.Keys.CopyTo(sorted, 0);
            Array.Sort(sorted);

            var ranks = new Dictionary<int, int>();
            var rank = 1;
            ranks.Add(sorted[0], 1);
            for (int i = 1; i < sorted.Length; i++)
            {
                int newRank = rank + frequencies[sorted[i - 1]];
                ranks.Add(sorted[i], newRank);
                rank = newRank;
            }

            int[] result = new int[input.Length];
            for (int i = 0; i < input.Length; i++)
            {
                result[i] = ranks[input[i]];
            }
            return result;
        }