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TrustPilotChallenge/WhiteRabbit/StringsProcessor.cs

64 lines
2.6 KiB

namespace WhiteRabbit
{
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using System.Numerics;
internal class StringsProcessor
{
public StringsProcessor(string sourceString, int maxWordsCount, IEnumerable<string> words)
{
var filteredSource = new string(sourceString.Where(ch => ch != ' ').ToArray());
this.VectorsConverter = new VectorsConverter(filteredSource);
// Dictionary of vectors to array of words represented by this vector
this.VectorsToWords = words
.Distinct()
.Select(word => new { word, vector = this.VectorsConverter.GetVector(word) })
.Where(tuple => tuple.vector != null)
.Select(tuple => new { tuple.word, vector = tuple.vector.Value })
.GroupBy(tuple => tuple.vector)
.ToDictionary(group => group.Key, group => group.Select(tuple => tuple.word).ToArray());
this.VectorsProcessor = new VectorsProcessor(
this.VectorsConverter.GetVector(filteredSource).Value,
maxWordsCount,
this.VectorsToWords.Keys,
this.VectorsConverter.GetString);
}
private VectorsConverter VectorsConverter { get; }
private VectorsProcessor VectorsProcessor { get; }
private Dictionary<Vector<byte>, string[]> VectorsToWords { get; }
public IEnumerable<string> GeneratePhrases()
{
// task of finding anagrams could be reduced to the task of finding sequences of dictionary vectors with the target sum
var sums = this.VectorsProcessor.GenerateSequences();
// converting sequences of vectors to the sequences of words...
var anagramsWords = sums
.Select(sum => ImmutableStack.Create(sum.Select(vector => this.VectorsToWords[vector]).ToArray()))
.SelectMany(this.Flatten)
.Select(stack => stack.ToArray());
return anagramsWords.Select(list => string.Join(" ", list));
}
// Converts e.g. pair of variants [[a, b, c], [d, e]] into all possible pairs: [[a, d], [a, e], [b, d], [b, e], [c, d], [c, e]]
private IEnumerable<ImmutableStack<T>> Flatten<T>(ImmutableStack<T[]> phrase)
{
if (phrase.IsEmpty)
{
return new[] { ImmutableStack.Create<T>() };
}
T[] wordVariants;
var newStack = phrase.Pop(out wordVariants);
return this.Flatten(newStack).SelectMany(remainder => wordVariants.Select(word => remainder.Push(word)));
}
}
}