Created
September 23, 2011 15:14
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taxes calculation
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| using System; | |
| using System.Collections.Generic; | |
| using System.Linq; | |
| using System.Text; | |
| namespace ConsoleApplication1 | |
| { | |
| class Program | |
| { | |
| private static TaxRate[] _entries = new TaxRate[] | |
| { | |
| new TaxRate(5070, 0.10m), | |
| new TaxRate(8660, 0.14m), | |
| new TaxRate(14070, 0.23m), | |
| new TaxRate(21240, 0.30m), | |
| new TaxRate(40230, 0.33m), | |
| new TaxRate(null, 0.45m), | |
| }; | |
| public static void Main() | |
| { | |
| var calculator = new TaxCalculator(_entries); | |
| var taxes = new decimal[] { 5000, 5800, 9000, 15000, 50000 }.Select(sum => calculator.GetTaxes(sum)); | |
| foreach (var sum in taxes) | |
| { | |
| Console.WriteLine(sum); | |
| } | |
| } | |
| } | |
| public class TaxCalculator | |
| { | |
| private TaxRate[] _policy; | |
| public TaxCalculator(TaxRate[] policy) | |
| { | |
| //TODO: Ensure that policy entries are ordered and the last one has open boundary value. | |
| _policy = policy; | |
| } | |
| public decimal GetTaxes(decimal sum) | |
| { | |
| if (sum < 0) | |
| throw new ArgumentException("Incorrect sum"); | |
| decimal result = 0; | |
| decimal previousBound = 0; | |
| foreach (var entry in _policy) | |
| { | |
| bool stop; | |
| decimal part = CalculatePart(sum, previousBound, entry, out stop); | |
| result += part; | |
| if (stop) break; | |
| //Will not affect correctness, not relevant for the last step. | |
| previousBound = entry.UpperBound ?? 0; | |
| } | |
| return result; | |
| } | |
| private decimal CalculatePart(decimal sum, decimal previousBound, TaxRate entry, out bool stop) | |
| { | |
| stop = false; | |
| decimal boundary = entry.UpperBound.HasValue ? entry.UpperBound.Value : decimal.MaxValue; | |
| decimal result; | |
| if (sum < boundary) | |
| { | |
| result = (sum - previousBound) * entry.Rate; | |
| stop = true; | |
| } | |
| else | |
| { | |
| result = (boundary - previousBound) * entry.Rate; | |
| } | |
| return result; | |
| } | |
| } | |
| public struct TaxRate | |
| { | |
| public decimal? UpperBound; | |
| public decimal Rate; | |
| public TaxRate(decimal? boundary, decimal rate) | |
| { | |
| UpperBound = boundary; | |
| Rate = rate; | |
| } | |
| } | |
| } |
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