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1 /*
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2 File: LLCell.d
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3
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4 Originally written by Doug Lea and released into the public domain.
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5 Thanks for the assistance and support of Sun Microsystems Labs, Agorics
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6 Inc, Loral, and everyone contributing, testing, and using this code.
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7
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8 History:
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9 Date Who What
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10 24Sep95 dl@cs.oswego.edu Create from tango.util.collection.d working file
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11
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12 */
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13
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14
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15 module tango.util.collection.impl.LLCell;
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16
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17 private import tango.util.collection.impl.Cell;
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18
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19 private import tango.util.collection.model.Comparator;
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20
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21 /**
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22 *
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23 *
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24 * LLCells extend Cells with standard linkedlist next-fields,
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25 * and provide a standard operations on them.
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26 * <P>
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27 * LLCells are pure implementation tools. They perform
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28 * no argument checking, no result screening, and no synchronization.
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29 * They rely on user-level classes (see for example LinkedList) to do such things.
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30 * Still, the class is made `public' so that you can use them to
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31 * build other kinds of collections or whatever, not just the ones
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32 * currently supported.
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33 *
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34 author: Doug Lea
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35 * @version 0.93
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36 *
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37 * <P> For an introduction to this package see <A HREF="index.html"> Overview </A>.
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38 **/
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39
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40 public class LLCell(T) : Cell!(T)
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41 {
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42 alias Comparator!(T) ComparatorT;
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43
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44
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45 protected LLCell next_;
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46
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47 /**
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48 * Return the next cell (or null if none)
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49 **/
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50
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51 public LLCell next()
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52 {
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53 return next_;
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54 }
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55
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56 /**
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57 * set to point to n as next cell
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58 * @param n, the new next cell
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59 **/
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60
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61 public void next(LLCell n)
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62 {
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63 next_ = n;
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64 }
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65
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66 public this (T v, LLCell n)
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67 {
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68 super(v);
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69 next_ = n;
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70 }
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71
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72 public this (T v)
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73 {
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74 this(v, null);
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75 }
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76
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77 public this ()
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78 {
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79 this(T.init, null);
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80 }
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81
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82
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83 /**
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84 * Splice in p between current cell and whatever it was previously
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85 * pointing to
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86 * @param p, the cell to splice
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87 **/
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88
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89 public final void linkNext(LLCell p)
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90 {
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91 if (p !is null)
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92 p.next_ = next_;
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93 next_ = p;
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94 }
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95
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96 /**
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97 * Cause current cell to skip over the current next() one,
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98 * effectively removing the next element from the list
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99 **/
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100
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101 public final void unlinkNext()
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102 {
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103 if (next_ !is null)
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104 next_ = next_.next_;
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105 }
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106
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107 /**
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108 * Linear search down the list looking for element (using T.equals)
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109 * @param element to look for
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110 * Returns: the cell containing element, or null if no such
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111 **/
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112
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113 public final LLCell find(T element)
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114 {
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115 for (LLCell p = this; p !is null; p = p.next_)
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116 if (p.element() == element)
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117 return p;
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118 return null;
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119 }
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120
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121 /**
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122 * return the number of cells traversed to find first occurrence
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123 * of a cell with element() element, or -1 if not present
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124 **/
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125
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126 public final int index(T element)
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127 {
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128 int i = 0;
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129 for (LLCell p = this; p !is null; p = p.next_)
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130 {
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131 if (p.element() == element)
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132 return i;
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133 else
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134 ++i;
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135 }
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136 return -1;
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137 }
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138
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139 /**
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140 * Count the number of occurrences of element in list
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141 **/
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142
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143 public final int count(T element)
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144 {
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145 int c = 0;
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146 for (LLCell p = this; p !is null; p = p.next_)
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147 if (p.element() == element)
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148 ++c;
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149 return c;
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150 }
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151
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152 /**
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153 * return the number of cells in the list
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154 **/
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155
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156 public final int _length()
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157 {
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158 int c = 0;
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159 for (LLCell p = this; p !is null; p = p.next_)
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160 ++c;
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161 return c;
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162 }
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163
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164 /**
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165 * return the cell representing the last element of the list
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166 * (i.e., the one whose next() is null
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167 **/
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168
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169 public final LLCell tail()
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170 {
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171 LLCell p = this;
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172 for ( ; p.next_ !is null; p = p.next_)
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173 {}
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174 return p;
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175 }
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176
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177 /**
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178 * return the nth cell of the list, or null if no such
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179 **/
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180
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181 public final LLCell nth(int n)
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182 {
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183 LLCell p = this;
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184 for (int i = 0; i < n; ++i)
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185 p = p.next_;
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186 return p;
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187 }
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188
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189
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190 /**
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191 * make a copy of the list; i.e., a new list containing new cells
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192 * but including the same elements in the same order
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193 **/
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194
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195 public final LLCell copyList()
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196 {
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197 LLCell newlist = null;
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198 newlist = duplicate();
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199 LLCell current = newlist;
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200
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201 for (LLCell p = next_; p !is null; p = p.next_)
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202 {
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203 current.next_ = p.duplicate();
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204 current = current.next_;
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205 }
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206 current.next_ = null;
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207 return newlist;
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208 }
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209
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210 /**
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211 * Clone is SHALLOW; i.e., just makes a copy of the current cell
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212 **/
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213
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214 private final LLCell duplicate()
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215 {
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216 return new LLCell(element(), next_);
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217 }
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218
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219 /**
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220 * Basic linkedlist merge algorithm.
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221 * Merges the lists head by fst and snd with respect to cmp
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222 * @param fst head of the first list
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223 * @param snd head of the second list
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224 * @param cmp a Comparator used to compare elements
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225 * Returns: the merged ordered list
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226 **/
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227
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228 public final static LLCell merge(LLCell fst, LLCell snd, ComparatorT cmp)
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229 {
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230 LLCell a = fst;
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231 LLCell b = snd;
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232 LLCell hd = null;
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233 LLCell current = null;
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234 for (;;)
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235 {
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236 if (a is null)
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237 {
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238 if (hd is null)
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239 hd = b;
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240 else
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241 current.next(b);
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242 return hd;
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243 }
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244 else
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245 if (b is null)
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246 {
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247 if (hd is null)
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248 hd = a;
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249 else
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250 current.next(a);
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251 return hd;
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252 }
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253
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254 int diff = cmp.compare(a.element(), b.element());
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255 if (diff <= 0)
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256 {
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257 if (hd is null)
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258 hd = a;
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259 else
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260 current.next(a);
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261 current = a;
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262 a = a.next();
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263 }
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264 else
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265 {
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266 if (hd is null)
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267 hd = b;
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268 else
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269 current.next(b);
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270 current = b;
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271 b = b.next();
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272 }
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273 }
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274 return null;
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275 }
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276
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277 /**
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278 * Standard list splitter, used by sort.
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279 * Splits the list in half. Returns the head of the second half
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280 * @param s the head of the list
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281 * Returns: the head of the second half
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282 **/
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283
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284 public final static LLCell split(LLCell s)
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285 {
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286 LLCell fast = s;
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287 LLCell slow = s;
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288
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289 if (fast is null || fast.next() is null)
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290 return null;
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291
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292 while (fast !is null)
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293 {
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294 fast = fast.next();
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295 if (fast !is null && fast.next() !is null)
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296 {
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297 fast = fast.next();
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298 slow = slow.next();
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299 }
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300 }
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301
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302 LLCell r = slow.next();
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303 slow.next(null);
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304 return r;
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305
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306 }
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307
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308 /**
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309 * Standard merge sort algorithm
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310 * @param s the list to sort
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311 * @param cmp, the comparator to use for ordering
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312 * Returns: the head of the sorted list
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313 **/
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314
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315 public final static LLCell mergeSort(LLCell s, ComparatorT cmp)
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316 {
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317 if (s is null || s.next() is null)
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318 return s;
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319 else
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320 {
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321 LLCell right = split(s);
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322 LLCell left = s;
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323 left = mergeSort(left, cmp);
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324 right = mergeSort(right, cmp);
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325 return merge(left, right, cmp);
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326 }
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327 }
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328
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329 }
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330
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