1 //===-- Support/EquivalenceClasses.h ----------------------------*- C++ -*-===//
3 // Generic implementation of equivalence classes and implementation of
4 // union-find algorithms A not-so-fancy implementation: 2 level tree i.e root
5 // and one more level Overhead of a union = size of the equivalence class being
6 // attached Overhead of a find = 1.
8 //===----------------------------------------------------------------------===//
10 #ifndef SUPPORT_EQUIVALENCECLASSES_H
11 #define SUPPORT_EQUIVALENCECLASSES_H
16 template <class ElemTy>
17 class EquivalenceClasses {
18 // Maps each element to the element that is the leader of its
20 std::map<ElemTy, ElemTy> Elem2ECLeaderMap;
22 // Make Element2 the leader of the union of classes Element1 and Element2
23 // Element1 and Element2 are presumed to be leaders of their respective
24 // equivalence classes.
25 void attach(ElemTy Element1, ElemTy Element2) {
26 for (typename std::map<ElemTy, ElemTy>::iterator ElemI =
27 Elem2ECLeaderMap.begin(), ElemE = Elem2ECLeaderMap.end();
28 ElemI != ElemE; ++ElemI) {
29 if (ElemI->second == Element1)
30 Elem2ECLeaderMap[ElemI->first] = Element2;
36 void addElement (ElemTy NewElement) {
37 if (Elem2ECLeaderMap.find(NewElement) == Elem2ECLeaderMap.end())
38 Elem2ECLeaderMap[NewElement] = NewElement;
41 ElemTy findClass(ElemTy Element) {
42 if (Elem2ECLeaderMap.find(Element) == Elem2ECLeaderMap.end())
45 return Elem2ECLeaderMap[Element];
48 /// Attach the set with Element1 to the set with Element2 adding Element1 and
49 /// Element2 to the set of equivalence classes if they are not there already.
50 /// Implication: Make Element1 the element in the smaller set.
51 void unionSetsWith(ElemTy Element1, ElemTy Element2) {
52 // If either Element1 or Element2 does not already exist, include it
53 if (Elem2ECLeaderMap.find(Element1) == Elem2ECLeaderMap.end())
54 Elem2ECLeaderMap[Element1] = Element1;
55 if (Elem2ECLeaderMap.find(Element2) == Elem2ECLeaderMap.end())
56 Elem2ECLeaderMap[Element2] = Element2;
58 attach(Elem2ECLeaderMap[Element1], Elem2ECLeaderMap[Element2]);
61 // Returns a vector containing all the elements in the equivalent class
63 std::vector<ElemTy> getEqClass(ElemTy Element1) {
64 std::vector<ElemTy> EqClass;
66 if (Elem2ECLeaderMap.find(EqClass) == Elem2ECLeaderMap.end())
69 ElemTy classLeader = Elem2ECLeaderMap[Element1];
70 for (typename std::map<ElemTy, ElemTy>::iterator ElemI =
71 Elem2ECLeaderMap.begin(), ElemE = Elem2ECLeaderMap.end();
72 ElemI != ElemE; ++ElemI) {
73 if (ElemI->second == classLeader)
74 EqClass.push_back(ElemI->first);
80 std::map<ElemTy, ElemTy>& getLeaderMap() {
81 return Elem2ECLeaderMap ;