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