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// -*- c++ -*- //
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#ifndef HUGO_UNION_FIND_H
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#define HUGO_UNION_FIND_H
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#include <vector>
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#include <utility>
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namespace hugo {
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template <typename T, typename TIntMap>
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class UnionFind {
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public:
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typedef T ElementType;
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typedef std::pair<int,int> PairType;
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private:
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std::vector<PairType> data;
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TIntMap& map;
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public:
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UnionFind(TIntMap& m) : map(m) {}
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int whichComponent(T a)
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{
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int comp0 = map.get(a);
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if (comp0 < 0) {
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return insertNewElement(a);
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}
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int comp = comp0;
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int next;
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while ( (next = data[comp].first) != comp) {
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comp = next;
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}
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while ( (next = data[comp0].first) != comp) {
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data[comp0].first = comp;
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comp0 = next;
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}
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return comp;
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}
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int insertNewElement(T a)
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{
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int n = data.size();
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data.push_back(make_pair(n, 1));
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map.set(a,n);
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return n;
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}
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bool joinComponents(T a, T b)
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{
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int ca = whichComponent(a);
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int cb = whichComponent(b);
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if ( ca == cb )
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return false;
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if ( data[ca].second > data[cb].second ) {
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data[cb].first = ca;
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data[ca].second += data[cb].second;
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}
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else {
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data[ca].first = cb;
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data[cb].second += data[ca].second;
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}
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return true;
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}
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int componentSize(T a)
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{
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int ca = whichComponent(a);
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return data[ca].second;
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}
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};
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} //namespace hugo
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#endif //HUGO_UNION_FIND_H
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