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Efficient Brute Force generator that can be consumed by foreach. Replace contents of Program.cs in your .NET 5 project with the following code and run.
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| using System; | |
| foreach (var text in new BruteForceEnumerable(2, "abc")) | |
| Console.WriteLine(text.ToString()); | |
| public class BruteForceEnumerable | |
| { | |
| private readonly int _maxTextLength; | |
| private readonly string _characters; | |
| public BruteForceEnumerable(int maxTextLength, string characters) | |
| { | |
| _maxTextLength = maxTextLength > 0 | |
| ? maxTextLength | |
| : throw new ArgumentOutOfRangeException(nameof(maxTextLength), maxTextLength, | |
| "Value must be greater than 0."); | |
| _characters = string.IsNullOrEmpty(characters) | |
| ? throw new ArgumentException("Value cannot be null or empty string.", nameof(characters)) | |
| : characters; | |
| } | |
| public Enumerator GetEnumerator() => new Enumerator(this); | |
| public class Enumerator | |
| { | |
| private readonly BruteForceEnumerable _enumerable; | |
| private readonly char[] _textBuffer; | |
| private readonly int[] _indices; | |
| private int _position; | |
| internal Enumerator(BruteForceEnumerable enumerable) | |
| { | |
| _enumerable = enumerable; | |
| _textBuffer = new char[_enumerable._maxTextLength]; | |
| _indices = new int[_enumerable._maxTextLength]; | |
| _position = 0; | |
| } | |
| public ReadOnlySpan<char> Current => _textBuffer.AsSpan(0, _position + 1); | |
| public bool MoveNext() => MoveNext(_position); | |
| private bool MoveNext(int position) | |
| { | |
| if (_indices[position] < _enumerable._characters.Length) | |
| { | |
| _textBuffer[position] = _enumerable._characters[_indices[position]]; | |
| _indices[position]++; | |
| return true; | |
| } | |
| _textBuffer[position] = _enumerable._characters[0]; | |
| _indices[position] = 1; | |
| return position > 0 | |
| ? MoveNext(position - 1) | |
| : ++_position < _enumerable._maxTextLength | |
| ? MoveNext(_position) | |
| : false; | |
| } | |
| } | |
| } | |
| // Output: | |
| // a | |
| // b | |
| // c | |
| // aa | |
| // ab | |
| // ac | |
| // ba | |
| // bb | |
| // bc | |
| // ca | |
| // cb | |
| // cc |
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