leetcode401

public class Solution
    {
        /// <summary>
        /// 将二进制字符串转为十进制数字
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        private int BinToInt(string s)
        {
            var len = s.Length;
            int[] bins = new int[len];

            int sum = 0;

            for (int i = 0; i < len; i++)
            {
                int n = Convert.ToInt32(s[i].ToString());
                int mi = len - i - 1;
                sum += n * Convert.ToInt32(Math.Pow(2, mi));
            }

            return sum;
        }

        /// <summary>
        /// 将十进制数字转换为二进制字符串
        /// </summary>
        /// <param name="n"></param>
        /// <returns></returns>
        private string IntToBin(int n)
        {
            StringBuilder sb = new StringBuilder();
            do
            {
                var s = (n % 2).ToString();
                sb.Append(s);
                n = n / 2;
            } while (n != 0);

            var list = sb.ToString().Reverse();
            sb.Clear();
            foreach (var c in list)
            {
                sb.Append(c);
            }
            return sb.ToString();
        }

        //key表示1的个数，value是对应的可能的数值
        Dictionary<int, List<int>> HourDic = new Dictionary<int, List<int>>();
        Dictionary<int, List<int>> MinDic = new Dictionary<int, List<int>>();

        public IList<string> ReadBinaryWatch(int num)
        {
            //将从0到11的数字依次放入HourDic中
            for (int i = 0; i <= 11; i++)
            {
                //将数字依据1的个数存入不同的组
                var s = IntToBin(i);
                var countOne = 0;
                foreach (var c in s)
                {
                    if (c == '1')
                    {
                        countOne++;
                    }
                }
                if (!HourDic.ContainsKey(countOne))
                {
                    HourDic.Add(countOne, new List<int>() { i });
                }
                else
                {
                    HourDic[countOne].Add(i);
                }
            }

            //将从0到59的数字依次放入MinDic中
            for (int i = 0; i <= 59; i++)
            {
                var s = IntToBin(i);
                var countOne = 0;
                foreach (var c in s)
                {
                    if (c == '1')
                    {
                        countOne++;
                    }
                }
                if (!MinDic.ContainsKey(countOne))
                {
                    MinDic.Add(countOne, new List<int>() { i });
                }
                else
                {
                    MinDic[countOne].Add(i);
                }
            }

            IList<string> list = new List<string>();

            for (int i = 0; i <= num; i++)
            {
                //i用于小时，
                //j用于时间，
                int j = num - i;
                StringBuilder sb = new StringBuilder();
                if (HourDic.ContainsKey(i) && MinDic.ContainsKey(j))
                {
                    //列出可能的小时
                    var list1 = HourDic[i];//用于存储所有可能的小时

                    //列出可能的分钟
                    var list2 = MinDic[j];//用于存储所有可能的分钟

                    //做笛卡尔乘积，存入list
                    foreach (var l1 in list1)
                    {
                        foreach (var l2 in list2)
                        {
                            sb.Append(l1.ToString());
                            sb.Append(":");
                            if (l2 < 10)
                            {
                                sb.Append("0");
                            }
                            sb.Append(l2.ToString());
                            list.Add(sb.ToString());
                            sb.Clear();
                        }
                    }
                }
            }

            foreach (var l in list)
            {
                Console.WriteLine(l);
            }

            return list;
        }
    }

https://leetcode.com/problems/binary-watch/#/description