union_find.c

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/*
 * See Licensing and Copyright notice in naev.h
 */
#include "union_find.h"
 
#include "array.h"

void unionfind_init( UnionFind *uf, int n )
{
   uf->parent = array_create_size( int, n );
   uf->rank   = array_create_size( int, n );
   for ( int i = 0; i < n; i++ ) {
      array_push_back( &uf->parent, i );
      array_push_back( &uf->rank, 0 );
   }
}

void unionfind_free( UnionFind *uf )
{
   array_free( uf->parent );
   uf->parent = NULL;
   array_free( uf->rank );
   uf->rank = NULL;
}

void unionfind_union( UnionFind *uf, int x, int y )
{
   x = unionfind_find( uf, x );
   y = unionfind_find( uf, y );
   if ( uf->rank[x] > uf->rank[y] )
      uf->parent[y] = x;
   else {
      uf->parent[x] = y;
      if ( uf->rank[x] == uf->rank[y] )
         uf->rank[y]++;
   }
}

int unionfind_find( UnionFind *uf, int x )
{
   if ( uf->parent[x] != x )
      uf->parent[x] = unionfind_find( uf, uf->parent[x] );
   return uf->parent[x];
}

int *unionfind_findall( UnionFind *uf )
{
   int *a = array_create( int );
   for ( int i = 0; i < array_size( uf->parent ); i++ )
      if ( uf->parent[i] == i )
         array_push_back( &a, i );
   return a;
}