create present value module

Algorithms.Tests/Financial/PresentValueTests.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using Algorithms.Financial;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace Algorithms.Tests.Financial;
+
+public static class PresentValueTests
+{
+    [Test]
+    public static void Present_Value_General_Tests()
+    {
+        PresentValue.Calculate(0.13, [10.0, 20.70, -293.0, 297.0])
+            .Should()
+            .Be(4.69);
+
+        PresentValue.Calculate(0.07, [-109129.39, 30923.23, 15098.93, 29734.0, 39.0])
+            .Should()
+            .Be(-42739.63);
+
+        PresentValue.Calculate(0.07, [109129.39, 30923.23, 15098.93, 29734.0, 39.0])
+            .Should()
+            .Be(175519.15);
+
+        PresentValue.Calculate(0.0, [109129.39, 30923.23, 15098.93, 29734.0, 39.0])
+            .Should()
+            .Be(184924.55);
+    }
+
+    [Test]
+    public static void Present_Value_Exception_Tests()
+    {
+        Assert.Throws<ArgumentException>(() => PresentValue.Calculate(-1.0, [10.0, 20.70, -293.0, 297.0]));
+        Assert.Throws<ArgumentException>(() => PresentValue.Calculate(1.0, []));
+    }
+}

Algorithms/Financial/PresentValue.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Algorithms.Financial;
+
+/// <summary>
+/// PresentValue is the value of an expected income stream determined as of the date of valuation.
+/// </summary>
+public static class PresentValue
+{
+    public static double Calculate(double discountRate, List<double> cashFlows)
+    {
+        if (discountRate < 0)
+        {
+            throw new ArgumentException("Discount rate cannot be negative");
+        }
+
+        if (cashFlows == null || cashFlows.Count == 0)
+        {
+            throw new ArgumentException("Cash flows list cannot be empty");
+        }
+
+        double presentValue = cashFlows.Select((t, i) => t / Math.Pow(1 + discountRate, i)).Sum();
+
+        return Math.Round(presentValue, 2);
+    }
+}