ft_ls/libft/ft_lst_merge_sort.c
2017-03-30 05:10:37 +03:00

68 lines
1.1 KiB
C

#include "libft.h"
static t_list *merge(t_list *a, t_list *b, int (*cmp)())
{
t_list *result;
result = NULL;
if (a == NULL)
return(b);
else if (b == NULL)
return(a);
if (cmp(a->content, b->content))
{
result = a;
result->next = merge(a->next, b, cmp);
}
else
{
result = b;
result->next = merge(a, b->next, cmp);
}
return(result);
}
static void split(t_list *source, t_list **front_ptr, t_list **back_ptr)
{
t_list *fast;
t_list *slow;
if (source==NULL || source->next==NULL)
{
*front_ptr = source;
*back_ptr = NULL;
}
else
{
slow = source;
fast = source->next;
while (fast != NULL)
{
fast = fast->next;
if (fast != NULL)
{
slow = slow->next;
fast = fast->next;
}
}
*front_ptr = source;
*back_ptr = slow->next;
slow->next = NULL;
}
}
void ft_lst_merge_sort(t_list **head_ptr, int (*cmp)())
{
t_list *head;
t_list *a;
t_list *b;
head = *head_ptr;
if ((head == NULL) || (head->next == NULL))
return;
split(head, &a, &b);
ft_lst_merge_sort(&a, cmp);
ft_lst_merge_sort(&b, cmp);
*head_ptr = merge(a, b, cmp);
}