实例介绍
【实例简介】
调用示例：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | //数组列表 string[] array = { "01", "02", "03", "04", "05", "06", "07", "08", "09", "10" };//在其中选择6个数字int lowerIndex = 6;var combinations = new Facet.Combinatorics.Combinations<String>( array, lowerIndex, Facet.Combinatorics.GenerateOption.WithoutRepetition);List<string> list = new List<string>();foreach (IList<String> combis in combinations){ string[] arr = new string[combis.Count]; combis.CopyTo(arr,0); String combi = String.Join(" ",arr ); //Console.WriteLine(combi); list.Add(combi);}//将组合结果总数以及具体值 输出MessageBox.Show(list.Count.ToString() "\r\n" string.Join(",\r\n",list.ToArray())); |
【实例截图】
【核心代码】
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 | using System;using System.Collections.Generic;using System.Text;namespace Facet.Combinatorics { /// <summary> /// Combinations defines a meta-collection, typically a list of lists, of all possible /// subsets of a particular size from the set of values. This list is enumerable and /// allows the scanning of all possible combinations using a simple foreach() loop. /// Within the returned set, there is no prescribed order. This follows the mathematical /// concept of choose. For example, put 10 dominoes in a hat and pick 5. The number of possible /// combinations is defined as "10 choose 5", which is calculated as (10!) / ((10 - 5)! * 5!). /// </summary> /// <remarks> /// The MetaCollectionType parameter of the constructor allows for the creation of /// two types of sets, those with and without repetition in the output set when /// presented with repetition in the input set. /// /// When given a input collect {A B C} and lower index of 2, the following sets are generated: /// MetaCollectionType.WithRepetition => /// {A A}, {A B}, {A C}, {B B}, {B C}, {C C} /// MetaCollectionType.WithoutRepetition => /// {A B}, {A C}, {B C} /// /// Input sets with multiple equal values will generate redundant combinations in proprotion /// to the likelyhood of outcome. For example, {A A B B} and a lower index of 3 will generate: /// {A A B} {A A B} {A B B} {A B B} /// </remarks> /// <typeparam name="T">The type of the values within the list.</typeparam> public class Combinations<T> : IMetaCollection<T> { #region Constructors /// <summary> /// No default constructor, must provided a list of values and size. /// </summary> protected Combinations() { ; } /// <summary> /// Create a combination set from the provided list of values. /// The upper index is calculated as values.Count, the lower index is specified. /// Collection type defaults to MetaCollectionType.WithoutRepetition /// </summary> /// <param name="values">List of values to select combinations from.</param> /// <param name="lowerIndex">The size of each combination set to return.</param> public Combinations(IList<T> values, int lowerIndex) { Initialize(values, lowerIndex, GenerateOption.WithoutRepetition); } /// <summary> /// Create a combination set from the provided list of values. /// The upper index is calculated as values.Count, the lower index is specified. /// </summary> /// <param name="values">List of values to select combinations from.</param> /// <param name="lowerIndex">The size of each combination set to return.</param> /// <param name="type">The type of Combinations set to generate.</param> public Combinations(IList<T> values, int lowerIndex, GenerateOption type) { Initialize(values, lowerIndex, type); } #endregion #region IEnumerable Interface /// <summary> /// Gets an enumerator for collecting the list of combinations. /// </summary> /// <returns>The enumerator.</returns> public IEnumerator<IList<T>> GetEnumerator() { return new Enumerator(this); } /// <summary> /// Gets an enumerator for collecting the list of combinations. /// </summary> /// <returns>The enumerator.returns> System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return new Enumerator(this); } #endregion #region Enumerator Inner Class /// <summary> /// The enumerator that enumerates each meta-collection of the enclosing Combinations class. /// </summary> public class Enumerator : IEnumerator<IList<T>> { #region Constructors /// <summary> /// Construct a enumerator with the parent object. /// </summary> /// <param name="source">The source combinations object.</param> public Enumerator(Combinations<T> source) { myParent = source; myPermutationsEnumerator = (Permutations<bool>.Enumerator)myParent.myPermutations.GetEnumerator(); } #endregion #region IEnumerator interface /// <summary> /// Resets the combinations enumerator to the first combination. /// </summary> public void Reset() { myPermutationsEnumerator.Reset(); } /// <summary> /// Advances to the next combination of items from the set. /// </summary> /// <returns>True if successfully moved to next combination, False if no more unique combinations exist.</returns> /// <remarks> /// The heavy lifting is done by the permutations object, the combination is generated /// by creating a new list of those items that have a true in the permutation parrellel array. /// </remarks> public bool MoveNext() { bool ret = myPermutationsEnumerator.MoveNext(); myCurrentList = null; return ret; } /// <summary> /// The current combination /// </summary> public IList<T> Current { get { ComputeCurrent(); return myCurrentList; } } /// <summary> /// The current combination /// </summary> object System.Collections.IEnumerator.Current { get { ComputeCurrent(); return myCurrentList; } } /// <summary> /// Cleans up non-managed resources, of which there are none used here. /// </summary> public void Dispose() { ; } #endregion #region Heavy Lifting Members /// <summary> /// The only complex function of this entire wrapper, ComputeCurrent() creates /// a list of original values from the bool permutation provided. /// The exception for accessing current (InvalidOperationException) is generated /// by the call to .Current on the underlying enumeration. /// </summary> /// <remarks> /// To compute the current list of values, the underlying permutation object /// which moves with this enumerator, is scanned differently based on the type. /// The items have only two values, true and false, which have different meanings: /// /// For type WithoutRepetition, the output is a straightforward subset of the input array. /// E.g. 6 choose 3 without repetition /// Input array: {A B C D E F} /// Permutations: {0 1 0 0 1 1} /// Generates set: {A C D } /// Note: size of permutation is equal to upper index. /// /// For type WithRepetition, the output is defined by runs of characters and when to /// move to the next element. /// E.g. 6 choose 5 with repetition /// Input array: {A B C D E F} /// Permutations: {0 1 0 0 1 1 0 0 1 1} /// Generates set: {A B B D D } /// Note: size of permutation is equal to upper index - 1 lower index. /// </remarks> private void ComputeCurrent() { if(myCurrentList == null) { myCurrentList = new List<T>(); int index = 0; IList<bool> currentPermutation = (IList<bool>)myPermutationsEnumerator.Current; for(int i = 0; i < currentPermutation.Count; i) { if(currentPermutation[i] == false) { myCurrentList.Add(myParent.myValues[index]); if(myParent.Type == GenerateOption.WithoutRepetition) { index; } } else { index; } } } } #endregion #region Data /// <summary> /// Parent object this is an enumerator for. /// </summary> private Combinations<T> myParent; /// <summary> /// The current list of values, this is lazy evaluated by the Current property. /// </summary> private List<T> myCurrentList; /// <summary> /// An enumertor of the parents list of lexicographic orderings. /// </summary> private Permutations<bool>.Enumerator myPermutationsEnumerator; #endregion } #endregion #region IMetaList Interface /// <summary> /// The number of unique combinations that are defined in this meta-collection. /// This value is mathematically defined as Choose(M, N) where M is the set size /// and N is the subset size. This is M! / (N! * (M-N)!). /// </summary> public long Count { get { return myPermutations.Count; } } /// <summary> /// The type of Combinations set that is generated. /// </summary> public GenerateOption Type { get { return myMetaCollectionType; } } /// <summary> /// The upper index of the meta-collection, equal to the number of items in the initial set. /// </summary> public int UpperIndex { get { return myValues.Count; } } /// <summary> /// The lower index of the meta-collection, equal to the number of items returned each iteration. /// </summary> public int LowerIndex { get { return myLowerIndex; } } #endregion #region Heavy Lifting Members /// <summary> /// Initialize the combinations by settings a copy of the values from the /// </summary> /// <param name="values">List of values to select combinations from.</param> /// <param name="lowerIndex">The size of each combination set to return.</param> /// <param name="type">The type of Combinations set to generate.</param> /// <remarks> /// Copies the array and parameters and then creates a map of booleans that will /// be used by a permutations object to refence the subset. This map is slightly /// different based on whether the type is with or without repetition. /// /// When the type is WithoutRepetition, then a map of upper index elements is /// created with lower index false's. /// E.g. 8 choose 3 generates: /// Map: {1 1 1 1 1 0 0 0} /// Note: For sorting reasons, false denotes inclusion in output. /// /// When the type is WithRepetition, then a map of upper index - 1 lower index /// elements is created with the falses indicating that the 'current' element should /// be included and the trues meaning to advance the 'current' element by one. /// E.g. 8 choose 3 generates: /// Map: {1 1 1 1 1 1 1 1 0 0 0} (7 trues, 3 falses). /// </remarks> private void Initialize(IList<T> values, int lowerIndex, GenerateOption type) { myMetaCollectionType = type; myLowerIndex = lowerIndex; myValues = new List<T>(); myValues.AddRange(values); List<bool> myMap = new List<bool>(); if(type == GenerateOption.WithoutRepetition) { for(int i = 0; i < myValues.Count; i) { if(i >= myValues.Count - myLowerIndex) { myMap.Add(false); } else { myMap.Add(true); } } } else { for(int i = 0; i < values.Count - 1; i) { myMap.Add(true); } for(int i = 0; i < myLowerIndex; i) { myMap.Add(false); } } myPermutations = new Permutations<bool>(myMap); } #endregion #region Data /// <summary> /// Copy of values object is intialized with, required for enumerator reset. /// </summary> private List<T> myValues; /// <summary> /// Permutations object that handles permutations on booleans for combination inclusion. /// </summary> private Permutations<bool> myPermutations; /// <summary> /// The type of the combination collection. /// </summary> private GenerateOption myMetaCollectionType; /// <summary> /// The lower index defined in the constructor. /// </summary> private int myLowerIndex; #endregion }} |
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