C++ Programming Code Examples
C++ > Data Structures and Algorithm Analysis in C++ Code Examples
Efficient implementation of disjoint sets algorithm
/* Efficient implementation of disjoint sets algorithm */
#include "DisjSets.h"
/**
* Construct the disjoint sets object.
* numElements is the initial number of disjoint sets.
*/
DisjSets::DisjSets( int numElements ) : s( numElements )
{
for( int i = 0; i < s.size( ); i++ )
s[ i ] = -1;
}
/**
* Union two disjoint sets.
* For simplicity, we assume root1 and root2 are distinct
* and represent set names.
* root1 is the root of set 1.
* root2 is the root of set 2.
*/
void DisjSets::unionSets( int root1, int root2 )
{
if( s[ root2 ] < s[ root1 ] ) // root2 is deeper
s[ root1 ] = root2; // Make root2 new root
else
{
if( s[ root1 ] == s[ root2 ] )
s[ root1 ]--; // Update height if same
s[ root2 ] = root1; // Make root1 new root
}
}
/**
* Perform a find.
* Error checks omitted again for simplicity.
* Return the set containing x.
*/
int DisjSets::find( int x ) const
{
if( s[ x ] < 0 )
return x;
else
return find( s[ x ] );
}
/**
* Perform a find with path compression.
* Error checks omitted again for simplicity.
* Return the set containing x.
*/
int DisjSets::find( int x )
{
if( s[ x ] < 0 )
return x;
else
return s[ x ] = find( s[ x ] );
}
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