93 lines
1.8 KiB
C++
93 lines
1.8 KiB
C++
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#include <stdlib.h>
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#include <stdio.h>
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#include <assert.h>
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#include "global.h"
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#include "neighbors.h"
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#include "dist.h"
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#include "heap.h"
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#include "err.h"
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namespace Flute {
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void mst2_package_init( long n )
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{
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allocate_heap( n );
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allocate_nn_arrays( n );
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}
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/****************************************************************************/
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/*
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*/
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void mst2_package_done()
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{
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deallocate_heap();
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deallocate_nn_arrays();
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}
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/****************************************************************************/
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/*
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*/
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void mst2
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(
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long n,
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Point* pt,
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long* parent
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)
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{
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long i, k, nn1;
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long d;
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long oct;
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long root = 0;
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extern nn_array* nn;
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// brute_force_nearest_neighbors( n, pt, nn );
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dq_nearest_neighbors( n, pt, nn );
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/*
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Binary heap implementation of Prim's algorithm.
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Runs in O(n*log(n)) time since at most 8n edges are considered
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*/
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heap_init( n );
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heap_insert( root, 0 );
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parent[root] = root;
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for( k = 0; k < n; k++ ) /* n points to be extracted from heap */
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{
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i = heap_delete_min();
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if (i<0) break;
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#ifdef DEBUG
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assert( i >= 0 );
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#endif
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/*
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pt[i] entered the tree, update heap keys for its neighbors
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*/
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for( oct = 0; oct < 8; oct++ )
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{
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nn1 = nn[i][oct];
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if( nn1 >= 0 )
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{
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d = dist( pt[i], pt[nn1] );
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if( in_heap(nn1) && (d < heap_key(nn1)) )
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{
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heap_decrease_key( nn1, d );
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parent[nn1] = i;
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}
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else if( never_seen(nn1) )
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{
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heap_insert( nn1, d );
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parent[nn1] = i;
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}
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}
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}
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}
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}
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/****************************************************************************/
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/****************************************************************************/
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} // namespace Flute
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