Snippets

Cameron Presley C# Constraint Solver

Updated by Cameron Presley
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File CSharpConstraintFinder.cs Modified

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 		return value % 2 == 0;
 	}
 }
+
 class FirstDigitMustEqualLastDigitConstraint : IConstraint
 {
 	public bool FollowsConstraint(int value)
Updated by Cameron Presley
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File CSharpConstraintFinder.cs Modified

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 		return value % 2 == 0;
 	}
 }
-class PalindromeConstraint : IConstraint
+class FirstDigitMustEqualLastDigitConstraint : IConstraint
 {
 	public bool FollowsConstraint(int value)
 	{
Created by Cameron Presley
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File CSharpConstraintFinder.cs Added

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+// Recommend running this in LINQPad
+void Main()
+{
+	var numbers = Enumerable.Range(0, 10000).ToList();
+	var constraints = new List<IConstraint>{new MustBeFourDigitsLongConstraint(), new MustBeEvenConstraint(), new PalindromeConstraint()};
+	
+	var constraintSolver = new ConstraintSolver();
+	var result = constraintSolver.FindValues(constraints, numbers.ToList());
+	
+	result.Dump();
+}
+
+public interface IConstraint
+{
+	bool FollowsConstraint(int value);
+}
+
+class MustBeFourDigitsLongConstraint : IConstraint
+{
+	public bool FollowsConstraint(int value)
+	{
+		return value.ToString().Length == 4;
+	}
+}
+
+class MustBeEvenConstraint : IConstraint
+{
+	public bool FollowsConstraint(int value)
+	{
+		return value % 2 == 0;
+	}
+}
+class PalindromeConstraint : IConstraint
+{
+	public bool FollowsConstraint(int value)
+	{
+		var valueString = value.ToString();
+		return valueString[0] == valueString[valueString.Length-1];
+	}
+}
+
+class ConstraintSolver
+{
+	public List<int> FindValues(List<IConstraint> constraints, List<int> values)
+	{
+		if (constraints == null) throw new ArgumentNullException("constraints");
+		if (values == null) throw new ArgumentNullException("values");
+		
+		var result = values;
+		foreach (var constraint in constraints)
+		{
+			result = result.Where(x => constraint.FollowsConstraint(x)).ToList();
+		}
+		return result;
+	}
+}
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