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union_find.hxx |

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3 /* Copyright 2008-2009 by Ullrich Koethe */
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35
36
37 #ifndef VIGRA_UNION_FIND_HXX
38 #define VIGRA_UNION_FIND_HXX
39
40 #include "config.hxx"
41 #include "error.hxx"
42 #include "array_vector.hxx"
43
44 namespace vigra {
45
46 namespace detail {
47
48 template <class T>
49 class UnionFindArray
50 {
51 typedef typename ArrayVector<T>::difference_type IndexType;
52 mutable ArrayVector<T> labels_;
53
54 public:
55 UnionFindArray(T next_free_label = 1)
56 {
57 for(T k=0; k <= next_free_label; ++k)
58 labels_.push_back(k);
59 }
60
61 T nextFreeLabel() const
62 {
63 return labels_.back();
64 }
65
66 T find(T label) const
67 {
68 T root = label;
69 while(root != labels_[(IndexType)root])
70 root = labels_[(IndexType)root];
71 // path compression
72 while(label != root)
73 {
74 T next = labels_[(IndexType)label];
75 labels_[(IndexType)label] = root;
76 label = next;
77 }
78 return root;
79 }
80
81 T makeUnion(T l1, T l2)
82 {
83 l1 = find(l1);
84 l2 = find(l2);
85 if(l1 <= l2)
86 {
87 labels_[(IndexType)l2] = l1;
88 return l1;
89 }
90 else
91 {
92 labels_[(IndexType)l1] = l2;
93 return l2;
94 }
95 }
96
97 T finalizeLabel(T label)
98 {
99 if(label == (T)labels_.size()-1)
100 {
101 // indeed a new region
102 vigra_invariant(label < NumericTraits<T>::max(),
103 "connected components: Need more labels than can be represented in the destination type.");
104 // create new back entry
105 labels_.push_back((T)labels_.size());
106 }
107 else
108 {
109 // no new label => reset the back entry of the label array
110 labels_.back() = (T)labels_.size()-1;
111 }
112 return label;
113 }
114
115 T makeNewLabel()
116 {
117 T label = labels_.back();
118 vigra_invariant(label < NumericTraits<T>::max(),
119 "connected components: Need more labels than can be represented in the destination type.");
120 labels_.push_back((T)labels_.size());
121 return label;
122 }
123
124 unsigned int makeContiguous()
125 {
126 // compress trees
127 unsigned int count = 0;
128 for(IndexType i=0; i<(IndexType)(labels_.size()-1); ++i)
129 {
130 if(labels_[i] == i)
131 {
132 labels_[i] = (T)count++;
133 }
134 else
135 {
136 labels_[i] = labels_[(IndexType)labels_[i]];
137 }
138 }
139 return count-1;
140 }
141
142 T operator[](T label) const
143 {
144 return labels_[(IndexType)label];
145 }
146 };
147
148 } // namespace detail
149
150 } // namespace vigra
151
152 #endif // VIGRA_UNION_FIND_HXX

© Ullrich Köthe (ullrich.koethe@iwr.uni-heidelberg.de) Heidelberg Collaboratory for Image Processing, University of Heidelberg, Germany | html generated using doxygen and Python vigra 1.10.0 (Mon Nov 18 2013)