71 lines
1.4 KiB
C++
71 lines
1.4 KiB
C++
// Copyright (C) 2002-2012 Nikolaus Gebhardt
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// This file is part of the "Irrlicht Engine".
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// For conditions of distribution and use, see copyright notice in irrlicht.h
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#ifndef __IRR_HEAPSORT_H_INCLUDED__
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#define __IRR_HEAPSORT_H_INCLUDED__
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#include "irrTypes.h"
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namespace irr
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{
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namespace core
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{
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//! Sinks an element into the heap.
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template<class T>
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inline void heapsink(T*array, s32 element, s32 max)
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{
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while ((element<<1) < max) // there is a left child
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{
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s32 j = (element<<1);
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if (j+1 < max && array[j] < array[j+1])
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j = j+1; // take right child
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if (array[element] < array[j])
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{
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T t = array[j]; // swap elements
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array[j] = array[element];
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array[element] = t;
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element = j;
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}
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else
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return;
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}
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}
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//! Sorts an array with size 'size' using heapsort.
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template<class T>
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inline void heapsort(T* array_, s32 size)
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{
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// for heapsink we pretent this is not c++, where
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// arrays start with index 0. So we decrease the array pointer,
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// the maximum always +2 and the element always +1
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T* virtualArray = array_ - 1;
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s32 virtualSize = size + 2;
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s32 i;
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// build heap
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for (i=((size-1)/2); i>=0; --i)
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heapsink(virtualArray, i+1, virtualSize-1);
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// sort array, leave out the last element (0)
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for (i=size-1; i>0; --i)
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{
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T t = array_[0];
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array_[0] = array_[i];
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array_[i] = t;
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heapsink(virtualArray, 1, i + 1);
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}
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}
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} // end namespace core
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} // end namespace irr
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#endif
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