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<a href="sparse__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_SPARSE_PERMUTATION_H_</span></div><div class="line"><a name="l00015"></a><span class="lineno"> 15</span> <span class="preprocessor">#define OR_TOOLS_ALGORITHMS_SPARSE_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 <string></span></div><div class="line"><a name="l00018"></a><span class="lineno"> 18</span> <span class="preprocessor">#include <vector></span></div><div class="line"><a name="l00019"></a><span class="lineno"> 19</span> </div><div class="line"><a name="l00020"></a><span class="lineno"> 20</span> <span class="preprocessor">#include "ortools/base/logging.h"</span></div><div class="line"><a name="l00021"></a><span class="lineno"> 21</span> </div><div class="line"><a name="l00022"></a><span class="lineno"> 22</span> <span class="keyword">namespace </span><a class="code" href="namespaceoperations__research.html">operations_research</a> {</div><div class="line"><a name="l00023"></a><span class="lineno"> 23</span> </div><div class="line"><a name="l00024"></a><span class="lineno"> 24</span> <span class="comment">// A compact representation for permutations of {0..N-1} that displaces few</span></div><div class="line"><a name="l00025"></a><span class="lineno"> 25</span> <span class="comment">// elements: it needs only O(K) memory for a permutation that displaces</span></div><div class="line"><a name="l00026"></a><span class="lineno"> 26</span> <span class="comment">// K elements.</span></div><div class="line"><a name="l00027"></a><span class="lineno"> 27</span> <span class="keyword">class </span>SparsePermutation {</div><div class="line"><a name="l00028"></a><span class="lineno"> 28</span>  <span class="keyword">public</span>:</div><div class="line"><a name="l00029"></a><span class="lineno"> 29</span>  <span class="keyword">explicit</span> SparsePermutation(<span class="keywordtype">int</span> size) : size_(size) {} <span class="comment">// Identity.</span></div><div class="line"><a name="l00030"></a><span class="lineno"> 30</span> </div><div class="line"><a name="l00031"></a><span class="lineno"> 31</span>  <span class="comment">// TODO(user,user): complete the reader API.</span></div><div class="line"><a name="l00032"></a><span class="lineno"> 32</span>  <span class="keywordtype">int</span> Size()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> size_; }</div><div class="line"><a name="l00033"></a><span class="lineno"> 33</span>  <span class="keywordtype">int</span> NumCycles()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> cycle_ends_.size(); }</div><div class="line"><a name="l00034"></a><span class="lineno"> 34</span> </div><div class="line"><a name="l00035"></a><span class="lineno"> 35</span>  <span class="comment">// Returns the "support" of this permutation; that is, the set of elements</span></div><div class="line"><a name="l00036"></a><span class="lineno"> 36</span>  <span class="comment">// displaced by it.</span></div><div class="line"><a name="l00037"></a><span class="lineno"> 37</span>  <span class="keyword">const</span> std::vector<int>& Support()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> cycles_; }</div><div class="line"><a name="l00038"></a><span class="lineno"> 38</span> </div><div class="line"><a name="l00039"></a><span class="lineno"> 39</span>  <span class="comment">// The permutation has NumCycles() cycles numbered 0 .. NumCycles()-1.</span></div><div class="line"><a name="l00040"></a><span class="lineno"> 40</span>  <span class="comment">// To iterate over cycle #i of the permutation, do this:</span></div><div class="line"><a name="l00041"></a><span class="lineno"> 41</span>  <span class="comment">// for (const int e : permutation.Cycle(i)) { ...</span></div><div class="line"><a name="l00042"></a><span class="lineno"> 42</span>  <span class="keyword">struct </span>Iterator;</div><div class="line"><a name="l00043"></a><span class="lineno"> 43</span>  Iterator Cycle(<span class="keywordtype">int</span> i) <span class="keyword">const</span>;</div><div class="line"><a name="l00044"></a><span class="lineno"> 44</span> </div><div class="line"><a name="l00045"></a><span class="lineno"> 45</span>  <span class="comment">// This is useful for iterating over the pair {element, image}</span></div><div class="line"><a name="l00046"></a><span class="lineno"> 46</span>  <span class="comment">// of a permutation:</span></div><div class="line"><a name="l00047"></a><span class="lineno"> 47</span>  <span class="comment">//</span></div><div class="line"><a name="l00048"></a><span class="lineno"> 48</span>  <span class="comment">// for (int c = 0; c < perm.NumCycles(); ++c) {</span></div><div class="line"><a name="l00049"></a><span class="lineno"> 49</span>  <span class="comment">// int element = LastElementInCycle(c);</span></div><div class="line"><a name="l00050"></a><span class="lineno"> 50</span>  <span class="comment">// for (int image : perm.Cycle(c)) {</span></div><div class="line"><a name="l00051"></a><span class="lineno"> 51</span>  <span class="comment">// // The pair is (element, image).</span></div><div class="line"><a name="l00052"></a><span class="lineno"> 52</span>  <span class="comment">// ...</span></div><div class="line"><a name="l00053"></a><span class="lineno"> 53</span>  <span class="comment">// element = image;</span></div><div class="line"><a name="l00054"></a><span class="lineno"> 54</span>  <span class="comment">// }</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">//</span></div><div class="line"><a name="l00057"></a><span class="lineno"> 57</span>  <span class="comment">// TODO(user): Provide a full iterator for this? Note that we have more</span></div><div class="line"><a name="l00058"></a><span class="lineno"> 58</span>  <span class="comment">// information with the loop above. Not sure it is needed though.</span></div><div class="line"><a name="l00059"></a><span class="lineno"> 59</span>  <span class="keywordtype">int</span> LastElementInCycle(<span class="keywordtype">int</span> i) <span class="keyword">const</span>;</div><div class="line"><a name="l00060"></a><span class="lineno"> 60</span> </div><div class="line"><a name="l00061"></a><span class="lineno"> 61</span>  <span class="comment">// To add a cycle to the permutation, repeatedly call AddToCurrentCycle()</span></div><div class="line"><a name="l00062"></a><span class="lineno"> 62</span>  <span class="comment">// with the cycle's orbit, then call CloseCurrentCycle();</span></div><div class="line"><a name="l00063"></a><span class="lineno"> 63</span>  <span class="comment">// This shouldn't be called on trivial cycles (of length 1).</span></div><div class="line"><a name="l00064"></a><span class="lineno"> 64</span>  <span class="keywordtype">void</span> AddToCurrentCycle(<span class="keywordtype">int</span> x);</div><div class="line"><a name="l00065"></a><span class="lineno"> 65</span>  <span class="keywordtype">void</span> CloseCurrentCycle();</div><div class="line"><a name="l00066"></a><span class="lineno"> 66</span> </div><div class="line"><a name="l00067"></a><span class="lineno"> 67</span>  <span class="comment">// Removes the cycles with given indices from the permutation. This</span></div><div class="line"><a name="l00068"></a><span class="lineno"> 68</span>  <span class="comment">// works in O(K) for a permutation displacing K elements.</span></div><div class="line"><a name="l00069"></a><span class="lineno"> 69</span>  <span class="keywordtype">void</span> RemoveCycles(<span class="keyword">const</span> std::vector<int>& cycle_indices);</div><div class="line"><a name="l00070"></a><span class="lineno"> 70</span> </div><div class="line"><a name="l00071"></a><span class="lineno"> 71</span>  <span class="comment">// Output all non-identity cycles of the permutation, sorted</span></div><div class="line"><a name="l00072"></a><span class="lineno"> 72</span>  <span class="comment">// lexicographically (each cycle is described starting by its smallest</span></div><div class="line"><a name="l00073"></a><span class="lineno"> 73</span>  <span class="comment">// element; and all cycles are sorted lexicographically against each other).</span></div><div class="line"><a name="l00074"></a><span class="lineno"> 74</span>  <span class="comment">// This isn't efficient; use for debugging only.</span></div><div class="line"><a name="l00075"></a><span class="lineno"> 75</span>  <span class="comment">// Example: "(1 4 3) (5 9) (6 8 7)".</span></div><div class="line"><a name="l00076"></a><span class="lineno"> 76</span>  std::string DebugString() <span class="keyword">const</span>;</div><div class="line"><a name="l00077"></a><span class="lineno"> 77</span> </div><div class="line"><a name="l00078"></a><span class="lineno"> 78</span>  <span class="keyword">private</span>:</div><div class="line"><a name="l00079"></a><span class="lineno"> 79</span>  <span class="keyword">const</span> <span class="keywordtype">int</span> size_;</div><div class="line"><a name="l00080"></a><span class="lineno"> 80</span>  std::vector<int> cycles_;</div><div class="line"><a name="l00081"></a><span class="lineno"> 81</span>  std::vector<int> cycle_ends_;</div><div class="line"><a name="l00082"></a><span class="lineno"> 82</span> };</div><div class="line"><a name="l00083"></a><span class="lineno"> 83</span> </div><div class="line"><a name="l00084"></a><span class="lineno"> 84</span> <span class="keyword">inline</span> <span class="keywordtype">void</span> SparsePermutation::AddToCurrentCycle(<span class="keywordtype">int</span> x) {</div><div class="line"><a name="l00085"></a><span class="lineno"> 85</span>  DCHECK_GE(x, 0);</div><div class="line"><a name="l00086"></a><span class="lineno"> 86</span>  DCHECK_LT(x, size_);</div><div class="line"><a name="l00087"></a><span class="lineno"> 87</span>  cycles_.push_back(x);</div><div class="line"><a name="l00088"></a><span class="lineno"> 88</span> }</div><div class="line"><a name="l00089"></a><span class="lineno"> 89</span> </div><div class="line"><a name="l00090"></a><span class="lineno"> 90</span> <span class="keyword">inline</span> <span class="keywordtype">void</span> SparsePermutation::CloseCurrentCycle() {</div><div class="line"><a name="l00091"></a><span class="lineno"> 91</span>  <span class="keywordflow">if</span> (cycle_ends_.empty()) {</div><div class="line"><a name="l00092"></a><span class="lineno"> 92</span>  DCHECK_GE(cycles_.size(), 2);</div><div class="line"><a name="l00093"></a><span class="lineno"> 93</span>  } <span class="keywordflow">else</span> {</div><div class="line"><a name="l00094"></a><span class="lineno"> 94</span>  DCHECK_GE(cycles_.size(), cycle_ends_.back() + 2);</div><div class="line"><a name="l00095"></a><span class="lineno"> 95</span>  }</div><div class="line"><a name="l00096"></a><span class="lineno"> 96</span>  cycle_ends_.push_back(cycles_.size());</div><div class="line"><a name="l00097"></a><span class="lineno"> 97</span> }</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="keyword">struct </span>SparsePermutation::Iterator {</div><div class="line"><a name="l00100"></a><span class="lineno"> 100</span>  <span class="comment">// These typedefs allow this iterator to be used within testing::ElementsAre.</span></div><div class="line"><a name="l00101"></a><span class="lineno"> 101</span>  <span class="keyword">typedef</span> <span class="keywordtype">int</span> value_type;</div><div class="line"><a name="l00102"></a><span class="lineno"> 102</span>  <span class="keyword">typedef</span> std::vector<int>::const_iterator const_iterator;</div><div class="line"><a name="l00103"></a><span class="lineno"> 103</span> </div><div class="line"><a name="l00104"></a><span class="lineno"> 104</span>  Iterator() {}</div><div class="line"><a name="l00105"></a><span class="lineno"> 105</span>  Iterator(<span class="keyword">const</span> std::vector<int>::const_iterator& b,</div><div class="line"><a name="l00106"></a><span class="lineno"> 106</span>  <span class="keyword">const</span> std::vector<int>::const_iterator& e)</div><div class="line"><a name="l00107"></a><span class="lineno"> 107</span>  : begin_(b), end_(e) {}</div><div class="line"><a name="l00108"></a><span class="lineno"> 108</span> </div><div class="line"><a name="l00109"></a><span class="lineno"> 109</span>  std::vector<int>::const_iterator begin()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> begin_; }</div><div class="line"><a name="l00110"></a><span class="lineno"> 110</span>  std::vector<int>::const_iterator end()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> end_; }</div><div class="line"><a name="l00111"></a><span class="lineno"> 111</span>  <span class="keyword">const</span> std::vector<int>::const_iterator begin_;</div><div class="line"><a name="l00112"></a><span class="lineno"> 112</span>  <span class="keyword">const</span> std::vector<int>::const_iterator end_;</div><div class="line"><a name="l00113"></a><span class="lineno"> 113</span> </div><div class="line"><a name="l00114"></a><span class="lineno"> 114</span>  <span class="keywordtype">int</span> size()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> end_ - begin_; }</div><div class="line"><a name="l00115"></a><span class="lineno"> 115</span> };</div><div class="line"><a name="l00116"></a><span class="lineno"> 116</span> </div><div class="line"><a name="l00117"></a><span class="lineno"> 117</span> <span class="keyword">inline</span> SparsePermutation::Iterator SparsePermutation::Cycle(<span class="keywordtype">int</span> i)<span class="keyword"> const </span>{</div><div class="line"><a name="l00118"></a><span class="lineno"> 118</span>  DCHECK_GE(i, 0);</div><div class="line"><a name="l00119"></a><span class="lineno"> 119</span>  DCHECK_LT(i, NumCycles());</div><div class="line"><a name="l00120"></a><span class="lineno"> 120</span>  <span class="keywordflow">return</span> Iterator(cycles_.begin() + (i == 0 ? 0 : cycle_ends_[i - 1]),</div><div class="line"><a name="l00121"></a><span class="lineno"> 121</span>  cycles_.begin() + cycle_ends_[i]);</div><div class="line"><a name="l00122"></a><span class="lineno"> 122</span> }</div><div class="line"><a name="l00123"></a><span class="lineno"> 123</span> </div><div class="line"><a name="l00124"></a><span class="lineno"> 124</span> <span class="keyword">inline</span> <span class="keywordtype">int</span> SparsePermutation::LastElementInCycle(<span class="keywordtype">int</span> i)<span class="keyword"> const </span>{</div><div class="line"><a name="l00125"></a><span class="lineno"> 125</span>  DCHECK_GE(i, 0);</div><div class="line"><a name="l00126"></a><span class="lineno"> 126</span>  DCHECK_LT(i, cycle_ends_.size());</div><div class="line"><a name="l00127"></a><span class="lineno"> 127</span>  DCHECK_GT(cycle_ends_[i], i == 0 ? 0 : cycle_ends_[i - 1]);</div><div class="line"><a name="l00128"></a><span class="lineno"> 128</span>  <span class="keywordflow">return</span> cycles_[cycle_ends_[i] - 1];</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_SPARSE_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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