leetcode949

public class Solution
    {
        public string LargestTimeFromDigits(int[] A)
        {
            var list = Perm(A, 0);
            var maxHour = -1;
            var maxMinute = -1;
            foreach (var nums in list)
            {
                var hour = nums[0].ToString() + nums[1].ToString();
                var minute = nums[2].ToString() + nums[3].ToString();
                var strtime = hour + ":" + minute;
                if (ValidTime(strtime))
                {
                    var Inthour = Convert.ToInt32(hour);
                    var IntMinute = Convert.ToInt32(minute);
                    if ((Inthour > maxHour) || (Inthour == maxHour && IntMinute >= maxMinute))
                    {
                        maxHour = Inthour;
                        maxMinute = IntMinute;
                    }
                }
            }
            if (maxHour >= 0)
            {
                var tempHour = maxHour.ToString();
                var tempMinute = maxMinute.ToString();
                if (tempHour.Length == 1)
                {
                    tempHour = "0" + tempHour;
                }
                if (tempMinute.Length == 1)
                {
                    tempMinute = "0" + tempMinute;
                }
                return tempHour + ":" + tempMinute;
            }
            else
            {
                return "";
            }
        }

        private void Swap<T>(ref T a, ref T b)
        {
            T t = a;
            a = b;
            b = t;
        }
        private IEnumerable<int[]> Perm(int[] arr, int pos)
        {
            if (pos == arr.Length)
            {
                yield return arr;
            }
            for (int i = pos; i < arr.Length; ++i)
            {
                Swap(ref arr[i], ref arr[pos]);
                foreach (var j in Perm(arr, pos + 1)) yield return j;
                Swap(ref arr[i], ref arr[pos]);
            }
        }


        /// <summary>
        /// 判断时间格式是否合法
        /// </summary>
        /// <param name="time"></param>
        /// <returns></returns>
        private bool ValidTime(string time)
        {
            var part = time.Split(':');
            var hour = Convert.ToInt32(part[0]);
            var minute = Convert.ToInt32(part[1]);
            if (hour >= 0 && hour <= 23 && minute >= 0 && minute <= 59)
            {
                return true;
            }
            return false;
        }
    }

这题又长又卵，没意思。