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/* ************************************************************************** */
/* */
/* ::: :::::::: */
/* ft_qsort.c :+: :+: :+: */
/* +:+ +:+ +:+ */
/* By: cacharle <marvin@42.fr> +#+ +:+ +#+ */
/* +#+#+#+#+#+ +#+ */
/* Created: 2020/01/19 07:25:51 by cacharle #+# #+# */
/* Updated: 2020/04/04 22:10:29 by charles ### ########.fr */
/* */
/* ************************************************************************** */
#include "libft_algo.h"
/*
** \brief Helper to create a new range
** \param lo Lower bound
** \param hi Higher bound
** \return Range struct (not allocated)
*/
static t_ftrange ft_range_new(int lo, int hi)
{
t_ftrange range;
range.lo = lo;
range.hi = hi;
return (range);
}
/*
** \brief Array partitionning,
** takes a pivot and place every element lower than it before
** and every element greater after
** \param base Partitioned array
** \param range Lower and upper bound
** \param width Single element size
** \param compar Comparison function
*/
static int ft_qsort_partition(void *base, t_ftrange range,
size_t width, t_ftcompar_func compar)
{
void *pivot;
int p;
int i;
pivot = base + (range.hi * width);
p = range.lo;
i = range.lo - 1;
while (++i < range.hi)
{
if (compar(base + (i * width), pivot) < 0)
{
ft_memswap(base + (i * width), base + (p * width), width);
p++;
}
}
ft_memswap(pivot, base + (p * width), width);
return (p);
}
/*
** \brief Qsort recursion function
** \param base Array to sort
** \param range Lower and upper bound which define the area to sort
** \param width Single element size
** \param compar Comparision function
*/
static void ft_qsort_rec(void *base, t_ftrange range,
size_t width, t_ftcompar_func compar)
{
int pivot;
if (range.lo >= range.hi)
return ;
pivot = ft_qsort_partition(base, range, width, compar);
ft_qsort_rec(base, ft_range_new(range.lo, pivot - 1), width, compar);
ft_qsort_rec(base, ft_range_new(pivot + 1, range.hi), width, compar);
}
/*
** \brief Sort an array using the Quick sort algorithm
** \param base Array to sort
** \param nel Number of element in the array
** \param width Size of each element
** \param compar Comparision function
*/
void ft_qsort(void *base, size_t nel, size_t width,
t_ftcompar_func compar)
{
if (width == 0 || nel < 2)
return ;
ft_qsort_rec(base, ft_range_new(0, nel - 1), width, compar);
}
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