MaxProfit【★★★★★】

        /// <summary>
        /// Solution
        /// 100/100
        /// </summary>
        /// <param name="A"></param>
        /// <returns></returns>
        public int solution(int[] A)
        {
            if (A.Length <= 1)
                return 0;
            int minPrice = A[0];
            int maxProfitSofar = 0;
            for (int i = 1; i < A.Length; i++)
            {
                maxProfitSofar = Math.Max(maxProfitSofar, A[i] - minPrice);
                minPrice = Math.Min(minPrice, A[i]);
            }
            return maxProfitSofar;
        }