leetcode405

public class Solution
    {
        string ConverToHex(string bit)
        {
            var s = "";
            switch (bit)
            {
                case "":
                    s = "";
                    break;
                case "":
                    s = "";
                    break;
                case "":
                    s = "";
                    break;
                case "":
                    s = "";
                    break;
                case "":
                    s = "";
                    break;
                case "":
                    s = "";
                    break;
                case "":
                    s = "";
                    break;
                case "":
                    s = "";
                    break;
                case "":
                    s = "";
                    break;
                case "":
                    s = "";
                    break;
                case "":
                    s = "a";
                    break;
                case "":
                    s = "b";
                    break;
                case "":
                    s = "c";
                    break;
                case "":
                    s = "d";
                    break;
                case "":
                    s = "e";
                    break;
                case "":
                    s = "f";
                    break;
            }
            return s;
        }

        public string ToHex(int num)
        {
            var fuhao = ;
            if (num < )
            {
                fuhao = -;
                num = num * (-);
            }

            //10进制转16进制，负数使用补码
            var bitAry = new string[];
            for (int i = ; i < bitAry.Length; i++)
            {
                bitAry[i] = "";
            }
            //STEP1:十进制转二进制
            int index = ;
            do
            {
                var x = num % ;
                bitAry[index++] = x.ToString();
                num = num / ;
            } while (num != );

            var list = bitAry.ToList();

            //STEP2:正数使用原码，负数转补码
            if (fuhao == -)
            {
                list.Clear();

                bitAry[bitAry.Length - ] = "";//符号为设置为0

                //计算反码
                StringBuilder sbFan = new StringBuilder();
                for (int i = ; i < bitAry.Length - ; i++)
                {
                    if (bitAry[i] == "")
                    {
                        sbFan.Append("");
                    }
                    else
                    {
                        sbFan.Append("");
                    }
                }
                sbFan.Append("");//index=31的是符号位

                //反码加1

                var fanma = sbFan.ToString();

                var step = ;
                var first = true;
                for (int i = ; i < fanma.Length - ; i++)
                {
                    var x = Convert.ToInt32(fanma[i].ToString());
                    if (first)
                    {
                        first = false;
                        x = (x + ) % ;
                        list.Add(x.ToString());
                        if (x == )
                        {
                            step = ;
                        }
                        else
                        {
                            step = ;
                        }
                    }
                    else
                    {
                        list.Add(((x + step) % ).ToString());
                        if (x ==  && step == )
                        {
                            step = ;
                        }
                        else
                        {
                            step = ;
                        }
                    }
                }
                list.Add("");
            }

            //STEP3:二进制转十六进制
            string result = "";

            if (fuhao == -)//负数
            {
                var temp = "";
                for (int i = ; i < list.Count; i++)
                {

                    if ((i + ) %  != )//0,1,2
                    {
                        temp = list[i] + temp;
                    }
                    else
                    {
                        temp = list[i] + temp;
                        var hex = ConverToHex(temp);
                        result = hex + result;
                        temp = "";
                    }
                }
            }
            else//正数
            {
                var temp = "";
                for (int i = ; i < list.Count; i++)
                {
                    if ((i + ) %  != )
                    {
                        temp = list[i] + temp;
                    }
                    else
                    {
                        temp = list[i] + temp;
                        var hex = ConverToHex(temp);
                        result = hex + result;
                        temp = "";
                    }

                }

            }

            var notZeroIndex = -;
            for (int i = ; i < result.Length; i++)
            {
                if (result[i] != '')
                {
                    notZeroIndex = i;
                    break;
                }
            }
            if (notZeroIndex > )
            {
                result = result.Substring(notZeroIndex);
            }

            if (result == "")
            {
                result = "";
            }

            return result;
        }
    }

https://leetcode.com/problems/convert-a-number-to-hexadecimal/#/description