ft_ls/libft/ft_lst_merge_sort.c

75 lines
1.2 KiB
C

#include "libft.h"
t_list *SortedMerge(t_list *a, t_list *b)
{
t_list *result;
result = NULL;
if (a == NULL)
return(b);
else if (b==NULL)
return(a);
/* Pick either a or b, and recur */
if (a->data <= b->data)
{
result = a;
result->next = SortedMerge(a->next, b);
}
else
{
result = b;
result->next = SortedMerge(a, b->next);
}
return(result);
}
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);
/* Recursively sort the sublists */
ft_lst_merge_sort(&a, cmp);
ft_lst_merge_sort(&b, cmp);
/* answer = merge the two sorted lists together */
*head_ptr = SortedMerge(a, b);
}