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TrustPilotChallenge/WhiteRabbit/VectorsConverter.cs

47 lines
1.6 KiB

namespace WhiteRabbit
{
using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
/// <summary>
/// Converts strings to vectors containing chars count, based on a source string.
/// E.g. for source string "abc", string "a" is converted to [1, 0, 0], while string "bcb" is converted to [0, 2, 1].
/// </summary>
internal sealed class VectorsConverter
{
public VectorsConverter(byte[] sourceString)
{
var rawNumberOfOccurrences = sourceString.GroupBy(ch => ch).ToDictionary(group => group.Key, group => group.Count());
this.IntToChar = rawNumberOfOccurrences.OrderBy(kvp => kvp.Key).Select(kvp => kvp.Key).ToArray();
if (this.IntToChar.Length > Vector<byte>.Count)
{
throw new ArgumentException($"String should not contain more than {Vector<byte>.Count} different characters", nameof(sourceString));
}
this.CharToInt = Enumerable.Range(0, this.IntToChar.Length).ToDictionary(i => this.IntToChar[i], i => i);
}
private Dictionary<byte, int> CharToInt { get; }
private byte[] IntToChar { get; }
public Vector<byte>? GetVector(byte[] word)
{
if (word.Any(ch => !this.CharToInt.ContainsKey(ch)))
{
return null;
}
var arr = new byte[Vector<byte>.Count];
foreach (var ch in word)
{
arr[this.CharToInt[ch]]++;
}
return new Vector<byte>(arr);
}
}
}