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158
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1 using Implab;
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2 using System;
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3 using System.Collections.Generic;
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4 using System.Diagnostics;
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5 using System.Linq;
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6
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7 namespace Implab.Parsing {
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8 public class DFADefinition : IDFADefinition {
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9 readonly List<DFAStateDescriptior> m_states;
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10
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11 public const int INITIAL_STATE = 1;
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12 public const int UNREACHEBLE_STATE = 0;
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13
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14 DFAStateDescriptior[] m_statesArray;
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15 readonly int m_alpabetSize;
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16
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17 public DFADefinition(int alphabetSize) {
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18 m_states = new List<DFAStateDescriptior>();
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19 m_alpabetSize = alphabetSize;
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20
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21 m_states.Add(new DFAStateDescriptior());
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22 }
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23
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24 public DFAStateDescriptior[] States {
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25 get {
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26 if (m_statesArray == null)
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27 m_statesArray = m_states.ToArray();
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28 return m_statesArray;
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29 }
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30 }
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31
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32 public bool InitialStateIsFinal {
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33 get {
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34 return m_states[INITIAL_STATE].final;
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35 }
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36 }
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37
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38 public int AddState() {
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39 var index = m_states.Count;
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40 m_states.Add(new DFAStateDescriptior {
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41 final = false,
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42 transitions = new int[AlphabetSize]
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43 });
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44 m_statesArray = null;
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45
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46 return index;
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47 }
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48
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49 public int AddState(int[] tag) {
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50 var index = m_states.Count;
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51 bool final = tag != null && tag.Length != 0;
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52 m_states.Add(new DFAStateDescriptior {
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53 final = final,
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54 transitions = new int[AlphabetSize],
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55 tag = final ? tag : null
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56 });
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57 m_statesArray = null;
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58 return index;
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59 }
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60
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61 public void DefineTransition(int s1,int s2, int symbol) {
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62 Safe.ArgumentInRange(s1, 0, m_states.Count-1, "s1");
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63 Safe.ArgumentInRange(s2, 0, m_states.Count-1, "s2");
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64 Safe.ArgumentInRange(symbol, 0, AlphabetSize-1, "symbol");
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65
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66 m_states[s1].transitions[symbol] = s2;
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67 }
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68
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69 public void Optimize<TA>(IDFADefinition minimalDFA,IAlphabet<TA> sourceAlphabet, IAlphabet<TA> minimalAlphabet) {
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70 Safe.ArgumentNotNull(minimalDFA, "minimalDFA");
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71 Safe.ArgumentNotNull(minimalAlphabet, "minimalAlphabet");
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72
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73 var setComparer = new CustomEqualityComparer<HashSet<int>>(
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74 (x, y) => x.SetEquals(y),
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75 (s) => s.Sum(x => x.GetHashCode())
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76 );
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77
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78 var arrayComparer = new CustomEqualityComparer<int[]>(
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79 (x,y) => (new HashSet<int>(x)).SetEquals(new HashSet<int>(y)),
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80 (a) => a.Sum(x => x.GetHashCode())
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81 );
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82
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83 var optimalStates = new HashSet<HashSet<int>>(setComparer);
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84 var queue = new HashSet<HashSet<int>>(setComparer);
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85
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86 foreach (var g in Enumerable
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87 .Range(INITIAL_STATE, m_states.Count-1)
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88 .Select(i => new {
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89 index = i,
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90 descriptor = m_states[i]
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91 })
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92 .Where(x => x.descriptor.final)
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93 .GroupBy(x => x.descriptor.tag, arrayComparer)
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94 ) {
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95 optimalStates.Add(new HashSet<int>(g.Select(x => x.index)));
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96 }
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97
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98 var state = new HashSet<int>(
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99 Enumerable
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100 .Range(INITIAL_STATE, m_states.Count - 1)
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101 .Where(i => !m_states[i].final)
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102 );
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103 optimalStates.Add(state);
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104 queue.Add(state);
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105
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106 while (queue.Count > 0) {
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107 var stateA = queue.First();
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108 queue.Remove(stateA);
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109
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110 for (int c = 0; c < AlphabetSize; c++) {
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111 var stateX = new HashSet<int>();
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112
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113 for(int s = 1; s < m_states.Count; s++) {
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114 if (stateA.Contains(m_states[s].transitions[c]))
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115 stateX.Add(s);
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116 }
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117
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118 foreach (var stateY in optimalStates.ToArray()) {
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119 if (stateX.Overlaps(stateY) && !stateY.IsSubsetOf(stateX)) {
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120 var stateR1 = new HashSet<int>(stateY);
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121 var stateR2 = new HashSet<int>(stateY);
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122
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123 stateR1.IntersectWith(stateX);
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124 stateR2.ExceptWith(stateX);
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125
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126 optimalStates.Remove(stateY);
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127 optimalStates.Add(stateR1);
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128 optimalStates.Add(stateR2);
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129
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130 if (queue.Contains(stateY)) {
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131 queue.Remove(stateY);
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132 queue.Add(stateR1);
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133 queue.Add(stateR2);
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134 } else {
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135 queue.Add(stateR1.Count <= stateR2.Count ? stateR1 : stateR2);
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136 }
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137 }
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138 }
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139 }
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140 }
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141
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142 // строим карты соотвествия оптимальных состояний с оригинальными
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143
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144 var initialState = optimalStates.Single(x => x.Contains(INITIAL_STATE));
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145
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146 // карта получения оптимального состояния по соотвествующему ему простому состоянию
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147 int[] reveseOptimalMap = new int[m_states.Count];
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148 // карта с индексами оптимальных состояний
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149 HashSet<int>[] optimalMap = new HashSet<int>[optimalStates.Count + 1];
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150 {
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151 optimalMap[0] = new HashSet<int>(); // unreachable state
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152 optimalMap[1] = initialState; // initial state
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153 foreach (var ss in initialState)
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154 reveseOptimalMap[ss] = 1;
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155
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156 int i = 2;
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157 foreach (var s in optimalStates) {
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158 if (s.SetEquals(initialState))
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159 continue;
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160 optimalMap[i] = s;
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161 foreach (var ss in s)
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162 reveseOptimalMap[ss] = i;
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163 i++;
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164 }
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165 }
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166
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167 // получаем минимальный алфавит
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168
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169 var minClasses = new HashSet<HashSet<int>>(setComparer);
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170 var alphaQueue = new Queue<HashSet<int>>();
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171 alphaQueue.Enqueue(new HashSet<int>(Enumerable.Range(0,AlphabetSize)));
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172
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173 for (int s = 1 ; s < optimalMap.Length; s++) {
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174 var newQueue = new Queue<HashSet<int>>();
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175
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176 foreach (var A in alphaQueue) {
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177 if (A.Count == 1) {
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178 minClasses.Add(A);
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179 continue;
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180 }
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181
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182 // различаем классы символов, которые переводят в различные оптимальные состояния
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183 // optimalState -> alphaClass
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184 var classes = new Dictionary<int, HashSet<int>>();
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185
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186 foreach (var term in A) {
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187 // ищем все переходы класса по символу term
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188 var s2 = reveseOptimalMap[
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189 optimalMap[s].Select(x => m_states[x].transitions[term]).FirstOrDefault(x => x != 0) // первое допустимое элементарное состояние, если есть
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190 ];
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191
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192 HashSet<int> A2;
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193 if (!classes.TryGetValue(s2, out A2)) {
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194 A2 = new HashSet<int>();
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195 newQueue.Enqueue(A2);
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196 classes[s2] = A2;
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197 }
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198 A2.Add(term);
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199 }
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200 }
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201
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202 if (newQueue.Count == 0)
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203 break;
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204 alphaQueue = newQueue;
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205 }
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206
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207 foreach (var A in alphaQueue)
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208 minClasses.Add(A);
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209
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210 var alphabetMap = sourceAlphabet.Reclassify(minimalAlphabet, minClasses);
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211
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212 // построение автомата
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213
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214 var states = new int[ optimalMap.Length ];
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215 states[0] = UNREACHEBLE_STATE;
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216
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217 for(var s = INITIAL_STATE; s < states.Length; s++) {
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218 var tags = optimalMap[s].SelectMany(x => m_states[x].tag ?? Enumerable.Empty<int>()).Distinct().ToArray();
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219 if (tags.Length > 0)
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220 states[s] = minimalDFA.AddState(tags);
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221 else
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222 states[s] = minimalDFA.AddState();
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223 }
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224
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225 Debug.Assert(states[INITIAL_STATE] == INITIAL_STATE);
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226
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227 for (int s1 = 1; s1 < m_states.Count; s1++) {
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228 for (int c = 0; c < AlphabetSize; c++) {
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229 var s2 = m_states[s1].transitions[c];
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230 if (s2 != UNREACHEBLE_STATE) {
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231 minimalDFA.DefineTransition(
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232 reveseOptimalMap[s1],
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233 reveseOptimalMap[s2],
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234 alphabetMap[c]
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235 );
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236 }
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237 }
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238 }
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239
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240 }
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241
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242 public void PrintDFA<TA>(IAlphabet<TA> alphabet) {
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243
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244 var reverseMap = alphabet.CreateReverseMap();
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245
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246 for (int i = 1; i < reverseMap.Length; i++) {
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247 Console.WriteLine("C{0}: {1}", i, String.Join(",", reverseMap[i]));
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248 }
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249
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250 for (int i = 1; i < m_states.Count; i++) {
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251 var s = m_states[i];
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252 for (int c = 0; c < AlphabetSize; c++)
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253 if (s.transitions[c] != UNREACHEBLE_STATE)
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254 Console.WriteLine("S{0} -{1}-> S{2}{3}", i, String.Join(",", reverseMap[c]), s.transitions[c], m_states[s.transitions[c]].final ? "$" : "");
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255 }
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256 }
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257
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258 public int AlphabetSize {
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259 get;
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260 }
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261 }
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262 }
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