71 lines
1.7 KiB
C#
71 lines
1.7 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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namespace AusPostCode {
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public static class BaseConversion {
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// honestly surprised c# doesn't do this out of the box
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private static readonly char[] Characters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-=".ToCharArray();
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// thanks to https://stackoverflow.com/a/35004409
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private static readonly Dictionary<char, int> CharacterIndices =
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Characters.Select((c, i) => new {Char = c, Index = i}).ToDictionary(c => c.Char, c => c.Index);
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public static string ToBase(int num, int numberBase) {
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if (numberBase > Characters.Length) {
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throw new ArgumentOutOfRangeException(
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nameof(numberBase),
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$"Base must be below {Characters.Length}"
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);
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}
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if (Math.Abs(num) == 0) {
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return num.ToString();
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}
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var digits = new List<char>();
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var negative = num < 0;
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while (num > 0) {
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digits.Add(Characters[num % numberBase]);
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num /= numberBase;
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}
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digits.Reverse();
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return (negative ? "-" : "") + string.Join("", digits);
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}
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public static int FromBase(string num, int numberBase) {
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if (numberBase > Characters.Length) {
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throw new ArgumentOutOfRangeException(
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nameof(numberBase),
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$"Base must be below {Characters.Length}"
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);
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}
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var negative = false;
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if (num.StartsWith("-")) {
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// it's a negative number
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negative = true;
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num = num.Substring(1);
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}
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var x = num.ToCharArray();
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var result = 0;
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// thanks to https://stackoverflow.com/a/35004409 again for this 0uo
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for (var i = 0; i < x.Length; i++) {
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result += CharacterIndices[x[i]] * (int) Math.Pow(numberBase, x.Length - i - 1);
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}
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if (negative) {
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result *= -1;
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}
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return result;
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}
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}
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}
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