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