| | 1 | | using MoreStructures.Utilities; |
| | 2 | |
|
| | 3 | | namespace MoreStructures.BurrowsWheelerTransform.Builders.LastFirstFinders; |
| | 4 | |
|
| | 5 | | /// <summary> |
| | 6 | | /// A <see cref="ILastFirstFinder"/> implementation which just iterates over <see cref="BWT"/> and its sorted version |
| | 7 | | /// <see cref="SortedBWT"/> every time. |
| | 8 | | /// </summary> |
| | 9 | | /// <remarks> |
| | 10 | | /// Each operation has Time Complexity = O(n) and Space Complexity = O(1), since no additional structure is precomputed |
| | 11 | | /// and/or stored. |
| | 12 | | /// </remarks> |
| | 13 | | public class NaiveFinder : ILastFirstFinder |
| | 14 | | { |
| | 15 | | /// <inheritdoc/> |
| 222 | 16 | | public IComparer<char> CharComparer { get; } |
| | 17 | |
|
| | 18 | | /// <inheritdoc/> |
| 2131 | 19 | | public RotatedTextWithTerminator BWT { get; } |
| | 20 | |
|
| | 21 | | /// <inheritdoc/> |
| 560 | 22 | | public RotatedTextWithTerminator SortedBWT { get; } |
| | 23 | |
|
| | 24 | | /// <summary> |
| | 25 | | /// Builds an instance of this finder, for the provided <paramref name="lastBWMColumn"/> and |
| | 26 | | /// <paramref name="firstBWMColumn"/>. Because both columns of the BWM are provided, no sorting happens. |
| | 27 | | /// </summary> |
| | 28 | | /// <param name="lastBWMColumn"> |
| | 29 | | /// The last column of the Burrows-Wheeler Matrix. Corresponds to the <see cref="BWT"/>. |
| | 30 | | /// </param> |
| | 31 | | /// <param name="firstBWMColumn"> |
| | 32 | | /// The first column of the Burrows-Wheeler Matrix. Corresponds to the <see cref="SortedBWT"/>. |
| | 33 | | /// </param> |
| 169 | 34 | | public NaiveFinder(RotatedTextWithTerminator lastBWMColumn, RotatedTextWithTerminator firstBWMColumn) |
| 169 | 35 | | { |
| 169 | 36 | | CharComparer = CharOrTerminatorComparer.Build(lastBWMColumn.Terminator); |
| 169 | 37 | | BWT = lastBWMColumn; |
| 169 | 38 | | SortedBWT = firstBWMColumn; |
| 169 | 39 | | } |
| | 40 | |
|
| | 41 | | private static int FindIndexOfNthOccurrenceInText( |
| | 42 | | RotatedTextWithTerminator text, char charToFind, int occurrenceRank) |
| 248 | 43 | | { |
| 248 | 44 | | if (occurrenceRank < 0) |
| 9 | 45 | | throw new ArgumentOutOfRangeException(nameof(occurrenceRank), $"Must be non-negative: {occurrenceRank}."); |
| | 46 | |
|
| 239 | 47 | | return Enumerable |
| 239 | 48 | | .Range(0, text.Length) |
| 1937 | 49 | | .Where(index => text[index] == charToFind) |
| 239 | 50 | | .Cast<int?>() |
| 239 | 51 | | .ElementAtOrDefault(occurrenceRank) |
| 239 | 52 | | ?? throw new ArgumentOutOfRangeException( |
| 239 | 53 | | $"Invalid {nameof(charToFind)} or {nameof(occurrenceRank)}: {charToFind}, {occurrenceRank}"); |
| 230 | 54 | | } |
| | 55 | |
|
| | 56 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 57 | | /// <remarks> |
| | 58 | | /// This implementation just iterates over <see cref="BWT"/> every time. |
| | 59 | | /// <br/> |
| | 60 | | /// Time Complexity = O(n). Space Complexity = O(1). |
| | 61 | | /// </remarks> |
| | 62 | | public virtual int FindIndexOfNthOccurrenceInBWT(int indexOfCharInBWT, int occurrenceRank) => |
| 32 | 63 | | FindIndexOfNthOccurrenceInText(BWT, BWT[indexOfCharInBWT], occurrenceRank); |
| | 64 | |
|
| | 65 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 66 | | /// <remarks> |
| | 67 | | /// This implementation just iterates over <see cref="SortedBWT"/> every time. |
| | 68 | | /// <br/> |
| | 69 | | /// Time Complexity = O(n). Space Complexity = O(1). |
| | 70 | | /// </remarks> |
| | 71 | | public virtual int FindIndexOfNthOccurrenceInSortedBWT(int indexOfCharInBWT, int occurrenceRank) => |
| 219 | 72 | | FindIndexOfNthOccurrenceInText(SortedBWT, BWT[indexOfCharInBWT], occurrenceRank); |
| | 73 | |
|
| | 74 | | private static int FindOccurrenceRankOfCharInText( |
| | 75 | | RotatedTextWithTerminator text, int indexOfCharInText) |
| 433 | 76 | | { |
| 433 | 77 | | if (indexOfCharInText < 0 || indexOfCharInText >= text.Length) |
| 6 | 78 | | throw new ArgumentOutOfRangeException(nameof(indexOfCharInText), $"Invalid value: {indexOfCharInText}"); |
| | 79 | |
|
| 427 | 80 | | return Enumerable |
| 427 | 81 | | .Range(0, indexOfCharInText) |
| 3654 | 82 | | .Count(index => text[index] == text[indexOfCharInText]); |
| 427 | 83 | | } |
| | 84 | |
|
| | 85 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 86 | | /// <remarks> |
| | 87 | | /// This implementation just iterates over <see cref="BWT"/> every time. |
| | 88 | | /// <br/> |
| | 89 | | /// Time Complexity = O(n). Space Complexity = O(1). |
| | 90 | | /// </remarks> |
| | 91 | | public virtual int FindOccurrenceRankOfCharInBWT(int indexOfCharInBWT) => |
| 424 | 92 | | FindOccurrenceRankOfCharInText(BWT, indexOfCharInBWT); |
| | 93 | |
|
| | 94 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 95 | | /// <remarks> |
| | 96 | | /// This implementation just iterates over <see cref="SortedBWT"/> every time. |
| | 97 | | /// <br/> |
| | 98 | | /// Time Complexity = O(n). Space Complexity = O(1). |
| | 99 | | /// </remarks> |
| | 100 | | public virtual int FindOccurrenceRankOfCharInSortedBWT(int indexOfCharInSortedBWT) => |
| 9 | 101 | | FindOccurrenceRankOfCharInText(SortedBWT, indexOfCharInSortedBWT); |
| | 102 | |
|
| | 103 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 104 | | /// <remarks> |
| | 105 | | /// First executes <see cref="FindOccurrenceRankOfCharInBWT(int)"/>, to find the occurrence rank of the char at |
| | 106 | | /// index <paramref name="indexOfCharInBWT"/> and then uses the last-to-first property to find the corresponding |
| | 107 | | /// char in <see cref="SortedBWT"/> by using <see cref="FindIndexOfNthOccurrenceInSortedBWT(int, int)"/>. |
| | 108 | | /// <br/> |
| | 109 | | /// Time and Space Complexity depends on the implementation of <see cref="FindOccurrenceRankOfCharInBWT(int)"/> and |
| | 110 | | /// <see cref="FindIndexOfNthOccurrenceInSortedBWT(int, int)"/>. |
| | 111 | | /// </remarks> |
| | 112 | | public virtual (int indexInSortedBWT, int occurrenceRank) LastToFirst(int indexOfCharInBWT) |
| 673 | 113 | | { |
| 673 | 114 | | var occurrenceRank = FindOccurrenceRankOfCharInBWT(indexOfCharInBWT); |
| 673 | 115 | | return (FindIndexOfNthOccurrenceInSortedBWT(indexOfCharInBWT, occurrenceRank), occurrenceRank); |
| 673 | 116 | | } |
| | 117 | | } |