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NikitaYermaksiriak
NikitaYermak
and
siriak
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Add Luhn algorithm (#195)
Co-authored-by: Andrii Siriak <siryaka@gmail.com>
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‎Algorithms.Tests/Other/LuhnTests.cs

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using NUnit.Framework;
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using Algorithms.Other;
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namespace Algorithms.Tests.Other
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{
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/// <summary>
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/// A class for testing the Luhn algorithm.
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/// </summary>
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public class LuhnTests
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{
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[Test]
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[TestCase("89014103211118510720")] // ICCID
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[TestCase("071052120")] // Social Security Code
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[TestCase("449125546588769")] // IMEI
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[TestCase("4417123456789113")] // Bank card
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public void ValidateTrue(string number)
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{
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// Arrange
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bool validate;
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// Act
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validate = Luhn.Validate(number);
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// Assert
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Assert.True(validate);
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}
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[Test]
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[TestCase("89012104211118510720")] // ICCID
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[TestCase("021053120")] // Social Security Code
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[TestCase("449145545588969")] // IMEI
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[TestCase("4437113456749113")] // Bank card
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public void ValidateFalse(string number)
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{
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// Arrange
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bool validate;
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// Act
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validate = Luhn.Validate(number);
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// Assert
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Assert.False(validate);
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}
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[Test]
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[TestCase("x9012104211118510720")] // ICCID
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[TestCase("0210x3120")] // Social Security Code
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[TestCase("44914554558896x")] // IMEI
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[TestCase("4437113456x49113")] // Bank card
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public void GetLostNum(string number)
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{
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// Arrange
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int lostNum;
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bool validate;
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// Act
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lostNum = Luhn.GetLostNum(number);
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validate = Luhn.Validate(number.Replace("x", lostNum.ToString()));
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// Assert
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Assert.True(validate);
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}
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}
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}

‎Algorithms/Other/Luhn.cs

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using System;
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using System.Linq;
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namespace Algorithms.Other
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{
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/// <summary>
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/// Luhn algorithm is a simple
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/// checksum formula used to validate
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/// a variety of identification numbers,
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/// such as credit card numbers.
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/// More information on the link:
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/// https://en.wikipedia.org/wiki/Luhn_algorithm.
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/// </summary>
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public static class Luhn
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{
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/// <summary>
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/// Checking the validity of a sequence of numbers.
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/// </summary>
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/// <param name="number">The number that will be checked for validity.</param>
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/// <returns>True: Number is valid.
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/// False: Number isn`t valid.</returns>
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public static bool Validate(string number) => GetSum(number) % 10 == 0;
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/// <summary>
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/// This algorithm only finds one number.
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/// In place of the unknown digit, put "x".
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/// </summary>
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/// <param name="number">The number in which to find the missing digit.</param>
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/// <returns>Missing digit.</returns>
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public static int GetLostNum(string number)
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{
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var lostIndex = number.Length - 1 - number.LastIndexOf("x", StringComparison.CurrentCultureIgnoreCase);
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var lostNum = GetSum(number.Replace("x", "0", StringComparison.CurrentCultureIgnoreCase)) * 9 % 10;
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// Case 1: If the index of the lost digit is even.
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if (lostIndex % 2 == 0)
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{
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return lostNum;
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}
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var tempLostNum = lostNum / 2;
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// Case 2: if the index of the lost digit isn`t even and that number <= 4.
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// Case 3: if the index of the lost digit isn`t even and that number > 4.
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return Validate(number.Replace("x", tempLostNum.ToString())) ? tempLostNum : (lostNum + 9) / 2;
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}
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/// <summary>
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/// Computes the sum found by the algorithm.
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/// </summary>
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/// <param name="number">The number for which the sum will be found.</param>
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/// <returns>Sum.</returns>
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private static int GetSum(string number)
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{
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var sum = 0;
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for (var i = 0; i < number.Length; i++)
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{
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var d = number[i] - '0';
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d = (i + number.Length) % 2 == 0
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? 2 * d
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: d;
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if (d > 9)
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{
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d -= 9;
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}
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sum += d;
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}
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return sum;
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}
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}
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}

‎C-Sharp.sln

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@@ -30,7 +30,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "DataStructures.Tests", "Dat
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EndProject
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Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Utilities", "Utilities\Utilities.csproj", "{3A41157D-296D-4BFC-A34E-91B5ED7F0905}"
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EndProject
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Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Utilities.Tests", "Utilities.Tests\Utilities.Tests.csproj", "{ED47E2E2-045C-41DD-B555-A64944D6C2F5}"
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Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Utilities.Tests", "Utilities.Tests\Utilities.Tests.csproj", "{ED47E2E2-045C-41DD-B555-A64944D6C2F5}"
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EndProject
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Global
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GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -42,22 +42,28 @@ Global
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{39174100-3A6E-45B2-9AA9-7C69764C0750}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
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{39174100-3A6E-45B2-9AA9-7C69764C0750}.Debug|Any CPU.Build.0 = Debug|Any CPU
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{39174100-3A6E-45B2-9AA9-7C69764C0750}.Release|Any CPU.Build.0 = Release|Any CPU
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{3A41157D-296D-4BFC-A34E-91B5ED7F0905}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
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{3A41157D-296D-4BFC-A34E-91B5ED7F0905}.Debug|Any CPU.Build.0 = Debug|Any CPU
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{3A41157D-296D-4BFC-A34E-91B5ED7F0905}.Release|Any CPU.ActiveCfg = Release|Any CPU
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{3A41157D-296D-4BFC-A34E-91B5ED7F0905}.Release|Any CPU.Build.0 = Release|Any CPU
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{ED47E2E2-045C-41DD-B555-A64944D6C2F5}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
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{ED47E2E2-045C-41DD-B555-A64944D6C2F5}.Debug|Any CPU.Build.0 = Debug|Any CPU
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{ED47E2E2-045C-41DD-B555-A64944D6C2F5}.Release|Any CPU.ActiveCfg = Release|Any CPU
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{ED47E2E2-045C-41DD-B555-A64944D6C2F5}.Release|Any CPU.Build.0 = Release|Any CPU
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{3A41157D-296D-4BFC-A34E-91B5ED7F0905}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
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{3A41157D-296D-4BFC-A34E-91B5ED7F0905}.Debug|Any CPU.Build.0 = Debug|Any CPU
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EndGlobalSection
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GlobalSection(SolutionProperties) = preSolution
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HideSolutionNode = FALSE

‎README.md

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* [Other](./Algorithms/Other/)
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* [Fermat Prime Checker](./Algorithms/Other/FermatPrimeChecker.cs)
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* [Sieve of Eratosthenes](./Algorithms/Other/SieveOfEratosthenes.cs)
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* [Luhn](./Algorithms/Other/Luhn.cs)
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* [Problems](./Algorithms/Problems/)
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* [Stable Marriage](./Algorithms/Problems/StableMarriage)
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* [Gale-Shapley](./Algorithms/Problems/StableMarriage/GaleShapley.cs)

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