BigInteger.ToBase62String

BigIntegerExtensions.cs

using System;
using System.Collections.Generic;
using System.Numerics;

public static class BigIntegerExtensions
{
	private static readonly char[] digits = new char[]
	{
		'0', '1', '2', '3', '4', '5', '6', '7',
		'8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
		'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
		'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
		'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D',
		'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
		'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
		'U', 'V', 'W', 'X', 'Y', 'Z'
	};
	public static string ToBase62String(this BigInteger param)
	{
		if (param == 0)
		{
			return param.ToString();
		}
		var baseNum = 62;
		var remainders = new List<char>();
		var (sign, quotient) = param < 0 ? ("-", (0 - param)) : (string.Empty, param);
		do
		{
			remainders.Insert(0, digits[(int)(quotient % baseNum)]);
			quotient /= baseNum;
		}
		while (quotient > 0);
		return $"{sign}{string.Join("", remainders.ToArray())}";
	}
}