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<a href="dynamic__permutation_8h.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">// Copyright 2010-2018 Google LLC</span></div><div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment">// Licensed under the Apache License, Version 2.0 (the "License");</span></div><div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment">// you may not use this file except in compliance with the License.</span></div><div class="line"><a name="l00004"></a><span class="lineno"> 4</span> <span class="comment">// You may obtain a copy of the License at</span></div><div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="comment">//</span></div><div class="line"><a name="l00006"></a><span class="lineno"> 6</span> <span class="comment">// http://www.apache.org/licenses/LICENSE-2.0</span></div><div class="line"><a name="l00007"></a><span class="lineno"> 7</span> <span class="comment">//</span></div><div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="comment">// Unless required by applicable law or agreed to in writing, software</span></div><div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="comment">// distributed under the License is distributed on an "AS IS" BASIS,</span></div><div class="line"><a name="l00010"></a><span class="lineno"> 10</span> <span class="comment">// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.</span></div><div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="comment">// See the License for the specific language governing permissions and</span></div><div class="line"><a name="l00012"></a><span class="lineno"> 12</span> <span class="comment">// limitations under the License.</span></div><div class="line"><a name="l00013"></a><span class="lineno"> 13</span> </div><div class="line"><a name="l00014"></a><span class="lineno"> 14</span> <span class="preprocessor">#ifndef OR_TOOLS_ALGORITHMS_DYNAMIC_PERMUTATION_H_</span></div><div class="line"><a name="l00015"></a><span class="lineno"> 15</span> <span class="preprocessor">#define OR_TOOLS_ALGORITHMS_DYNAMIC_PERMUTATION_H_</span></div><div class="line"><a name="l00016"></a><span class="lineno"> 16</span> </div><div class="line"><a name="l00017"></a><span class="lineno"> 17</span> <span class="preprocessor">#include <memory></span></div><div class="line"><a name="l00018"></a><span class="lineno"> 18</span> <span class="preprocessor">#include <set></span> <span class="comment">// TODO(user): remove when no longer used.</span></div><div class="line"><a name="l00019"></a><span class="lineno"> 19</span> <span class="preprocessor">#include <vector></span></div><div class="line"><a name="l00020"></a><span class="lineno"> 20</span> </div><div class="line"><a name="l00021"></a><span class="lineno"> 21</span> <span class="preprocessor">#include "ortools/base/logging.h"</span></div><div class="line"><a name="l00022"></a><span class="lineno"> 22</span> </div><div class="line"><a name="l00023"></a><span class="lineno"> 23</span> <span class="keyword">namespace </span><a class="code" href="namespaceoperations__research.html">operations_research</a> {</div><div class="line"><a name="l00024"></a><span class="lineno"> 24</span> </div><div class="line"><a name="l00025"></a><span class="lineno"> 25</span> <span class="keyword">class </span>SparsePermutation;</div><div class="line"><a name="l00026"></a><span class="lineno"> 26</span> </div><div class="line"><a name="l00027"></a><span class="lineno"> 27</span> <span class="comment">// Maintains a 'partial' permutation of [0..n-1] onto itself, with a dynamic</span></div><div class="line"><a name="l00028"></a><span class="lineno"> 28</span> <span class="comment">// API allowing it to be built incrementally, and allowing some backtracking.</span></div><div class="line"><a name="l00029"></a><span class="lineno"> 29</span> <span class="comment">// This is tuned for a specific usage by ./find_graph_symmetries.cc.</span></div><div class="line"><a name="l00030"></a><span class="lineno"> 30</span> <span class="comment">//</span></div><div class="line"><a name="l00031"></a><span class="lineno"> 31</span> <span class="comment">// RAM usage: as of 2014-04, this class needs less than:</span></div><div class="line"><a name="l00032"></a><span class="lineno"> 32</span> <span class="comment">// 32.125 * (n + 2 * support_size) bytes.</span></div><div class="line"><a name="l00033"></a><span class="lineno"> 33</span> <span class="keyword">class </span>DynamicPermutation {</div><div class="line"><a name="l00034"></a><span class="lineno"> 34</span>  <span class="keyword">public</span>:</div><div class="line"><a name="l00035"></a><span class="lineno"> 35</span>  <span class="comment">// Upon construction, every element i in [0..n-1] maps to itself.</span></div><div class="line"><a name="l00036"></a><span class="lineno"> 36</span>  <span class="keyword">explicit</span> DynamicPermutation(<span class="keywordtype">int</span> n);</div><div class="line"><a name="l00037"></a><span class="lineno"> 37</span> </div><div class="line"><a name="l00038"></a><span class="lineno"> 38</span>  <span class="keywordtype">int</span> Size()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> image_.size(); } <span class="comment">// Return the original "n".</span></div><div class="line"><a name="l00039"></a><span class="lineno"> 39</span> </div><div class="line"><a name="l00040"></a><span class="lineno"> 40</span>  <span class="comment">// Declares a set of mappings for this permutation: src[i] will map to dst[i].</span></div><div class="line"><a name="l00041"></a><span class="lineno"> 41</span>  <span class="comment">// Requirements that are DCHECKed:</span></div><div class="line"><a name="l00042"></a><span class="lineno"> 42</span>  <span class="comment">// - "src" and "dst" must have the same size.</span></div><div class="line"><a name="l00043"></a><span class="lineno"> 43</span>  <span class="comment">// - For all i, src[i] must not already be mapped to something.</span></div><div class="line"><a name="l00044"></a><span class="lineno"> 44</span>  <span class="comment">// - For all i, dst[i] must not already be the image of something.</span></div><div class="line"><a name="l00045"></a><span class="lineno"> 45</span>  <span class="comment">//</span></div><div class="line"><a name="l00046"></a><span class="lineno"> 46</span>  <span class="comment">// Complexity: amortized O(src.size()).</span></div><div class="line"><a name="l00047"></a><span class="lineno"> 47</span>  <span class="keywordtype">void</span> AddMappings(<span class="keyword">const</span> std::vector<int>& src, <span class="keyword">const</span> std::vector<int>& dst);</div><div class="line"><a name="l00048"></a><span class="lineno"> 48</span> </div><div class="line"><a name="l00049"></a><span class="lineno"> 49</span>  <span class="comment">// Undoes the last AddMappings() operation, and fills the "undone_mapping_src"</span></div><div class="line"><a name="l00050"></a><span class="lineno"> 50</span>  <span class="comment">// vector with the src of that last operation. This works like an undo stack.</span></div><div class="line"><a name="l00051"></a><span class="lineno"> 51</span>  <span class="comment">// For example, applying the sequence (Add, Add, Add, Undo, Add, Undo, Undo)</span></div><div class="line"><a name="l00052"></a><span class="lineno"> 52</span>  <span class="comment">// has exactly the same effect as applying the first Add() alone.</span></div><div class="line"><a name="l00053"></a><span class="lineno"> 53</span>  <span class="comment">// If you call this too may times (i.e. there is nothing left to undo), it is</span></div><div class="line"><a name="l00054"></a><span class="lineno"> 54</span>  <span class="comment">// simply a no-op.</span></div><div class="line"><a name="l00055"></a><span class="lineno"> 55</span>  <span class="comment">//</span></div><div class="line"><a name="l00056"></a><span class="lineno"> 56</span>  <span class="comment">// Complexity: same as the AddMappings() operation being undone.</span></div><div class="line"><a name="l00057"></a><span class="lineno"> 57</span>  <span class="keywordtype">void</span> UndoLastMappings(std::vector<int>* undone_mapping_src);</div><div class="line"><a name="l00058"></a><span class="lineno"> 58</span> </div><div class="line"><a name="l00059"></a><span class="lineno"> 59</span>  <span class="comment">// Makes the permutation back to the identity (i.e. like right after</span></div><div class="line"><a name="l00060"></a><span class="lineno"> 60</span>  <span class="comment">// construction).</span></div><div class="line"><a name="l00061"></a><span class="lineno"> 61</span>  <span class="comment">// Complexity: O(support size).</span></div><div class="line"><a name="l00062"></a><span class="lineno"> 62</span>  <span class="keywordtype">void</span> Reset();</div><div class="line"><a name="l00063"></a><span class="lineno"> 63</span> </div><div class="line"><a name="l00064"></a><span class="lineno"> 64</span>  <span class="keywordtype">int</span> ImageOf(<span class="keywordtype">int</span> i) <span class="keyword">const</span>; <span class="comment">// Complexity: one vector lookup.</span></div><div class="line"><a name="l00065"></a><span class="lineno"> 65</span> </div><div class="line"><a name="l00066"></a><span class="lineno"> 66</span>  <span class="comment">// Returns the union of all "src" ever given to AddMappings().</span></div><div class="line"><a name="l00067"></a><span class="lineno"> 67</span>  <span class="keyword">const</span> std::vector<int>& AllMappingsSrc()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> mapping_src_stack_; }</div><div class="line"><a name="l00068"></a><span class="lineno"> 68</span> </div><div class="line"><a name="l00069"></a><span class="lineno"> 69</span>  <span class="comment">// While the permutation is partially being built, the orbit of elements will</span></div><div class="line"><a name="l00070"></a><span class="lineno"> 70</span>  <span class="comment">// either form unclosed paths, or closed cycles. In the former case,</span></div><div class="line"><a name="l00071"></a><span class="lineno"> 71</span>  <span class="comment">// RootOf(i) returns the start of the path where i lies. If i is on a cycle,</span></div><div class="line"><a name="l00072"></a><span class="lineno"> 72</span>  <span class="comment">// RootOf(i) will return some element of its cycle (meaning that if i maps to</span></div><div class="line"><a name="l00073"></a><span class="lineno"> 73</span>  <span class="comment">// itself, RootOf(i) = i).</span></div><div class="line"><a name="l00074"></a><span class="lineno"> 74</span>  <span class="comment">//</span></div><div class="line"><a name="l00075"></a><span class="lineno"> 75</span>  <span class="comment">// Complexity: O(log(orbit size)) in average, assuming that the mappings are</span></div><div class="line"><a name="l00076"></a><span class="lineno"> 76</span>  <span class="comment">// added in a random order. O(orbit size) in the worst case.</span></div><div class="line"><a name="l00077"></a><span class="lineno"> 77</span>  <span class="keywordtype">int</span> RootOf(<span class="keywordtype">int</span> i) <span class="keyword">const</span>;</div><div class="line"><a name="l00078"></a><span class="lineno"> 78</span> </div><div class="line"><a name="l00079"></a><span class="lineno"> 79</span>  <span class="comment">// The exhaustive set of the 'loose end' of the incomplete cycles</span></div><div class="line"><a name="l00080"></a><span class="lineno"> 80</span>  <span class="comment">// (e.g., paths) built so far.</span></div><div class="line"><a name="l00081"></a><span class="lineno"> 81</span>  <span class="comment">// TODO(user): use a faster underlying container like SparseBitSet, and</span></div><div class="line"><a name="l00082"></a><span class="lineno"> 82</span>  <span class="comment">// tweak this API accordingly.</span></div><div class="line"><a name="l00083"></a><span class="lineno"> 83</span>  <span class="keyword">const</span> std::set<int>& LooseEnds()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> loose_ends_; }</div><div class="line"><a name="l00084"></a><span class="lineno"> 84</span> </div><div class="line"><a name="l00085"></a><span class="lineno"> 85</span>  <span class="comment">// Creates a SparsePermutation representing the current permutation.</span></div><div class="line"><a name="l00086"></a><span class="lineno"> 86</span>  <span class="comment">// Requirements: the permutation must only have cycles.</span></div><div class="line"><a name="l00087"></a><span class="lineno"> 87</span>  <span class="comment">//</span></div><div class="line"><a name="l00088"></a><span class="lineno"> 88</span>  <span class="comment">// Complexity: O(support size).</span></div><div class="line"><a name="l00089"></a><span class="lineno"> 89</span>  std::unique_ptr<SparsePermutation> CreateSparsePermutation() <span class="keyword">const</span>;</div><div class="line"><a name="l00090"></a><span class="lineno"> 90</span> </div><div class="line"><a name="l00091"></a><span class="lineno"> 91</span>  std::string DebugString() <span class="keyword">const</span>;</div><div class="line"><a name="l00092"></a><span class="lineno"> 92</span> </div><div class="line"><a name="l00093"></a><span class="lineno"> 93</span>  <span class="keyword">private</span>:</div><div class="line"><a name="l00094"></a><span class="lineno"> 94</span>  std::vector<int> image_;</div><div class="line"><a name="l00095"></a><span class="lineno"> 95</span>  <span class="comment">// ancestor_[i] isn't exactly RootOf(i): it might itself have an ancestor, and</span></div><div class="line"><a name="l00096"></a><span class="lineno"> 96</span>  <span class="comment">// so on.</span></div><div class="line"><a name="l00097"></a><span class="lineno"> 97</span>  std::vector<int> ancestor_;</div><div class="line"><a name="l00098"></a><span class="lineno"> 98</span> </div><div class="line"><a name="l00099"></a><span class="lineno"> 99</span>  <span class="comment">// The concatenation of all "src" ever given to AddMappings(), and their</span></div><div class="line"><a name="l00100"></a><span class="lineno"> 100</span>  <span class="comment">// sizes, to implement the undo stack. Note that "mapping_src_stack_" contains</span></div><div class="line"><a name="l00101"></a><span class="lineno"> 101</span>  <span class="comment">// exactly the support of the permutation.</span></div><div class="line"><a name="l00102"></a><span class="lineno"> 102</span>  std::vector<int> mapping_src_stack_;</div><div class="line"><a name="l00103"></a><span class="lineno"> 103</span>  std::vector<int> mapping_src_size_stack_;</div><div class="line"><a name="l00104"></a><span class="lineno"> 104</span> </div><div class="line"><a name="l00105"></a><span class="lineno"> 105</span>  <span class="comment">// See the homonymous accessor, above.</span></div><div class="line"><a name="l00106"></a><span class="lineno"> 106</span>  std::set<int> loose_ends_;</div><div class="line"><a name="l00107"></a><span class="lineno"> 107</span> </div><div class="line"><a name="l00108"></a><span class="lineno"> 108</span>  <span class="comment">// Used transiently by CreateSparsePermutation(). Its resting state is:</span></div><div class="line"><a name="l00109"></a><span class="lineno"> 109</span>  <span class="comment">// size=Size(), all elements are false.</span></div><div class="line"><a name="l00110"></a><span class="lineno"> 110</span>  <span class="keyword">mutable</span> std::vector<bool> tmp_mask_;</div><div class="line"><a name="l00111"></a><span class="lineno"> 111</span> };</div><div class="line"><a name="l00112"></a><span class="lineno"> 112</span> </div><div class="line"><a name="l00113"></a><span class="lineno"> 113</span> <span class="comment">// Forced-inline for the speed.</span></div><div class="line"><a name="l00114"></a><span class="lineno"> 114</span> <span class="keyword">inline</span> <span class="keywordtype">int</span> DynamicPermutation::ImageOf(<span class="keywordtype">int</span> i)<span class="keyword"> const </span>{</div><div class="line"><a name="l00115"></a><span class="lineno"> 115</span>  DCHECK_GE(i, 0);</div><div class="line"><a name="l00116"></a><span class="lineno"> 116</span>  DCHECK_LT(i, Size());</div><div class="line"><a name="l00117"></a><span class="lineno"> 117</span>  <span class="keywordflow">return</span> image_[i];</div><div class="line"><a name="l00118"></a><span class="lineno"> 118</span> }</div><div class="line"><a name="l00119"></a><span class="lineno"> 119</span> </div><div class="line"><a name="l00120"></a><span class="lineno"> 120</span> <span class="comment">// Forced-inline for the speed.</span></div><div class="line"><a name="l00121"></a><span class="lineno"> 121</span> <span class="keyword">inline</span> <span class="keywordtype">int</span> DynamicPermutation::RootOf(<span class="keywordtype">int</span> i)<span class="keyword"> const </span>{</div><div class="line"><a name="l00122"></a><span class="lineno"> 122</span>  DCHECK_GE(i, 0);</div><div class="line"><a name="l00123"></a><span class="lineno"> 123</span>  DCHECK_LT(i, Size());</div><div class="line"><a name="l00124"></a><span class="lineno"> 124</span>  <span class="keywordflow">while</span> (<span class="keyword">true</span>) {</div><div class="line"><a name="l00125"></a><span class="lineno"> 125</span>  <span class="keyword">const</span> <span class="keywordtype">int</span> j = ancestor_[i];</div><div class="line"><a name="l00126"></a><span class="lineno"> 126</span>  <span class="keywordflow">if</span> (j == i) <span class="keywordflow">return</span> i;</div><div class="line"><a name="l00127"></a><span class="lineno"> 127</span>  i = j;</div><div class="line"><a name="l00128"></a><span class="lineno"> 128</span>  }</div><div class="line"><a name="l00129"></a><span class="lineno"> 129</span> }</div><div class="line"><a name="l00130"></a><span class="lineno"> 130</span> </div><div class="line"><a name="l00131"></a><span class="lineno"> 131</span> } <span class="comment">// namespace operations_research</span></div><div class="line"><a name="l00132"></a><span class="lineno"> 132</span> </div><div class="line"><a name="l00133"></a><span class="lineno"> 133</span> <span class="preprocessor">#endif // OR_TOOLS_ALGORITHMS_DYNAMIC_PERMUTATION_H_</span></div><div class="ttc" id="namespaceoperations__research_html"><div class="ttname"><a href="namespaceoperations__research.html">operations_research</a></div><div class="ttdef"><b>Definition:</b> <a href="dense__doubly__linked__list_8h_source.html#l00021">dense_doubly_linked_list.h:21</a></div></div>
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