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// Copyright (C) 2005 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_SORt_
#define DLIB_SORt_
#include "algs.h"
#include <functional>
namespace dlib
{
// ----------------------------------------------------------------------------------------
template <
typename T,
typename compare
>
inline void qsort_array (
T& array,
unsigned long left,
unsigned long right,
const compare& comp
);
/*!
requires
- T implements operator[]
- the items in array must be comparable by comp where comp is a function
object with the same syntax as std::less<>
- the items in array must be swappable by a global swap()
- left and right are within the bounds of array
i.e. array[left] and array[right] are valid elements
- left <= right
ensures
- for all elements in #array between and including left and right the
ith element is < the i+1 element
- sorts using a quick sort algorithm
!*/
// ----------------------------------------------------------------------------------------
template <
typename T,
typename compare
>
void hsort_array (
T& array,
unsigned long left,
unsigned long right,
const compare& comp
);
/*!
requires
- T implements operator[]
- the items in array must be comparable by comp where comp is a function
object with the same syntax as std::less<>
- the items in array must be swappable by a global swap()
- left and right are within the bounds of array
i.e. array[left] and array[right] are valid elements
- left <= right
ensures
- for all elements in #array between and including left and right the
ith element is < the i+1 element
- sorts using a heapsort algorithm
!*/
// ----------------------------------------------------------------------------------------
template <
typename T,
typename compare
>
void isort_array (
T& array,
unsigned long left,
unsigned long right,
const compare& comp
);
/*!
requires
- T implements operator[]
- the items in array must be comparable by comp where comp is a function
object with the same syntax as std::less<>
- the items in array must be swappable by a global swap()
- left and right are within the bounds of array
i.e. array[left] and array[right] are valid elements
- left <= right
ensures
- for all elements in #array between and including left and right the
ith element is < the i+1 element
- sorts using an insertion sort algorithm
!*/
// ----------------------------------------------------------------------------------------
template <
typename T
>
inline void qsort_array (
T& array,
unsigned long left,
unsigned long right
);
/*!
requires
- T implements operator[]
- the items in array must be comparable by std::less
- the items in array must be swappable by a global swap()
- left and right are within the bounds of array
i.e. array[left] and array[right] are valid elements
- left <= right
ensures
- for all elements in #array between and including left and right the
ith element is < the i+1 element
- sorts using a quick sort algorithm
!*/
// ----------------------------------------------------------------------------------------
template <
typename T
>
void hsort_array (
T& array,
unsigned long left,
unsigned long right
);
/*!
requires
- T implements operator[]
- the items in array must be comparable by std::less
- the items in array must be swappable by a global swap()
- left and right are within the bounds of array
i.e. array[left] and array[right] are valid elements
- left <= right
ensures
- for all elements in #array between and including left and right the
ith element is < the i+1 element
- sorts using a heapsort algorithm
!*/
// ----------------------------------------------------------------------------------------
template <
typename T
>
void isort_array (
T& array,
unsigned long left,
unsigned long right
);
/*!
requires
- T implements operator[]
- the items in array must be comparable by std::less
- the items in array must be swappable by a global swap()
- left and right are within the bounds of array
i.e. array[left] and array[right] are valid elements
- left <= right
ensures
- for all elements in #array between and including left and right the
ith element is < the i+1 element
- sorts using an insertion sort algorithm
!*/
// ----------------------------------------------------------------------------------------
// ----------------------------------------------------------------------------------------
// IMPLEMENTATION DETAILS
// ----------------------------------------------------------------------------------------
// ----------------------------------------------------------------------------------------
namespace sort_helpers
{
template <typename T>
inline const std::less<T> comp (const T&)
{
return std::less<T>();
}
template <
typename T,
typename Y,
typename compare
>
inline unsigned long qsort_partition (
T& array,
Y& pivot,
const unsigned long left,
const unsigned long right,
const compare& comp
)
/*!
requires
- &pivot == &array[right]
- T implements operator[]
- the items in array must be comparable by comp
- left and right are within the bounts of the array
- left < right
ensures
- returns a number called partition_element such that:
- left <= partition_element <= right
- all elements in #array < #array[partition_element] have
indices >= left and < partition_element
- all elements in #array > #array[partition_element] have
indices > partition_element and <= right
!*/
{
DLIB_ASSERT (&pivot == &array[right] && left < right,
"\tunsigned long qsort_partition()"
<< "\n\t&pivot: " << &pivot
<< "\n\t&array[right]: " << &array[right]
<< "\n\tleft: " << left
<< "\n\tright: " << right );
exchange(array[(right-left)/2 +left],pivot);
unsigned long i = left;
for (unsigned long j = left; j < right; ++j)
{
if (comp(array[j] , pivot))
{
swap(array[i],array[j]);
++i;
}
}
exchange(array[i],pivot);
return i;
}
// ----------------------------------------------------------------------------------------
template <
typename T,
typename compare
>
void qsort_array_main (
T& array,
const unsigned long left,
const unsigned long right,
unsigned long depth_check,
const compare& comp
)
/*!
requires
- T implements operator[]
- the items in array must be comparable by comp
- the items in array must be swappable by a global swap()
- left and right are within the bounds of array
i.e. array[left] and array[right] are valid elements
ensures
- for all elements in #array between and including left and right the
ith element is < the i+1 element
- will only recurse about as deep as log(depth_check) calls
- sorts using a quick sort algorithm
!*/
{
if ( left < right)
{
if (right-left < 30 || depth_check == 0)
{
hsort_array(array,left,right,comp);
}
else
{
// The idea here is to only let quick sort go about log(N)
// calls deep before it kicks into something else.
depth_check >>= 1;
depth_check += (depth_check>>4);
unsigned long partition_element =
qsort_partition(array,array[right],left,right,comp);
if (partition_element > 0)
qsort_array_main(array,left,partition_element-1,depth_check,comp);
qsort_array_main(array,partition_element+1,right,depth_check,comp);
}
}
}
// ----------------------------------------------------------------------------------------
template <
typename T,
typename compare
>
void heapify (
T& array,
const unsigned long start,
const unsigned long end,
unsigned long i,
const compare& comp
)
/*!
requires
- T implements operator[]
- the items in array must be comparable by comp
- the items in array must be swappable by a global swap()
- start, end, and i are within the bounds of array
i.e. array[start], array[end], and array[i] are valid elements
- start <= i <= end
- array[i/2] is a max heap
- array[i/2+1] is a max heap
- start and end specify the range of the array we are working with.
ensures
- array[i] is now a max heap
!*/
{
DLIB_ASSERT (start <= i && i <= end,
"\tvoid heapify()"
<< "\n\tstart: " << start
<< "\n\tend: " << end
<< "\n\ti: " << i );
bool keep_going = true;
unsigned long left;
unsigned long right;
unsigned long largest;
while (keep_going)
{
keep_going = false;
left = (i<<1)+1-start;
right = left+1;
if (left <= end && comp(array[i] , array[left]))
largest = left;
else
largest = i;
if (right <= end && comp(array[largest] , array[right]))
largest = right;
if (largest != i)
{
exchange(array[i],array[largest]);
i = largest;
keep_going = true;
}
}
}
// ----------------------------------------------------------------------------------------
}
// ----------------------------------------------------------------------------------------
template <
typename T
>
inline void qsort_array (
T& array,
unsigned long left,
unsigned long right
)
{
using namespace sort_helpers;
qsort_array(array,left,right,comp(array[left]));
}
// ----------------------------------------------------------------------------------------
template <
typename T
>
void hsort_array (
T& array,
unsigned long left,
unsigned long right
)
{
using namespace sort_helpers;
hsort_array(array,left,right,comp(array[left]));
}
// ----------------------------------------------------------------------------------------
template <
typename T
>
void isort_array (
T& array,
unsigned long left,
unsigned long right
)
{
using namespace sort_helpers;
isort_array(array,left,right,comp(array[left]));
}
// ----------------------------------------------------------------------------------------
template <
typename T,
typename compare
>
void isort_array (
T& array,
const unsigned long left,
const unsigned long right,
const compare& comp
)
{
DLIB_ASSERT (left <= right,
"\tvoid isort_array()"
<< "\n\tleft: " << left
<< "\n\tright: " << right );
using namespace sort_helpers;
unsigned long pos;
for (unsigned long i = left+1; i <= right; ++i)
{
// everything from left to i-1 is sorted.
pos = i;
for (unsigned long j = i-1; comp(array[pos] , array[j]); --j)
{
exchange(array[pos],array[j]);
pos = j;
if (j == left)
break;
}
}
}
// ----------------------------------------------------------------------------------------
template <
typename T,
typename compare
>
void qsort_array (
T& array,
const unsigned long left,
const unsigned long right,
const compare& comp
)
{
DLIB_ASSERT (left <= right,
"\tvoid qsort_array()"
<< "\n\tleft: " << left
<< "\n\tright: " << right );
sort_helpers::qsort_array_main(array,left,right,right-left,comp);
}
// ----------------------------------------------------------------------------------------
template <
typename T,
typename compare
>
void hsort_array (
T& array,
const unsigned long left,
const unsigned long right,
const compare& comp
)
{
DLIB_ASSERT (left <= right,
"\tvoid hsort_array()"
<< "\n\tleft: " << left
<< "\n\tright: " << right );
if (right-left < 30)
{
isort_array(array,left,right,comp);
return;
}
// turn array into a max heap
for (unsigned long i = left+((right-left)>>1);; --i)
{
sort_helpers::heapify(array,left,right,i,comp);
if (i == left)
break;
}
// now sort the array
for (unsigned long i = right; i > left;)
{
exchange(array[i],array[left]);
sort_helpers::heapify(array,left,--i,left,comp);
}
}
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_SORt_
|
