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