fastunionfind.h

datastucutre and algorithms, application, in C

// union/find with weighting and path compaction

#ifndef fastUnionFind_
#define fastUnionFind_

#include <iostream>
#include "unionFindNode.h"

using namespace std;

class fastUnionFind
{
   public:
      fastUnionFind(int numberOfElements)
      {// Initialize numberOfElements trees, 1 element per set/class/tree.
        node = new unionFindNode[numberOfElements+1];
      }
      
      void unite(int rootA, int rootB)
      {// Combine trees with different roots rootA and rootB.
       // Use the weighting rule.
         if (node[rootA].parent < node[rootB].parent)
         {// rootA becomes subtree of rootB
            node[rootB].parent += node[rootA].parent;
            node[rootA].root = false;
            node[rootA].parent = rootB;
         }
         else
         {// rootB becomes subtree of rootA
            node[rootA].parent += node[rootB].parent;
            node[rootB].root = false;
            node[rootB].parent = rootA;
         }
      }
      
      int find(int theElement)
      {// Return root of tree containing theElement.
       // Compact path from theElement to root.
      
         // theRoot will eventually be the root of the tree
         int theRoot = theElement;
         while (!node[theRoot].root)
            theRoot = node[theRoot].parent;
         
         // compact pathe from theElement to theRoot
         int currentNode = theElement;  // start at theElement
         while (currentNode != theRoot)
         {
            int parentNode = node[currentNode].parent;
            node[currentNode].parent = theRoot;  // move to level 2
            currentNode = parentNode;            // moves to old parent 
         }
      
         return theRoot;
      }
      
   protected:
      unionFindNode *node;
};
#endif