-
Notifications
You must be signed in to change notification settings - Fork 0
/
mergelist2.c
137 lines (116 loc) · 2.63 KB
/
mergelist2.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
#include<stdio.h>
#include<stdlib.h>
struct node
{
int data;
struct node* next;
};
struct node* SortedMerge(struct node* a, struct node* b);
void FrontBackSplit(struct node* source, struct node** frontRef, struct node** backRef);
void MergeSort(struct node** headRef)
{
struct node* head = *headRef;
struct node* a;
struct node* b;
if((head == NULL) || (head->next == NULL))
{
return;
}
FrontBackSplit(head, &a, &b);
MergeSort(&a);
MergeSort(&b);
*headRef = SortedMerge(a,b);
}
struct node* SortedMerge(struct node* a, struct node* b)
{
struct node* result = NULL;
if(a==NULL)
return(b);
else if(b==NULL)
return(a);
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 FrontBackSplit(struct node* source,
struct node** frontRef, struct node** backRef)
{
struct node* fast;
struct node* slow;
if (source==NULL || source->next==NULL)
{
/* length < 2 cases */
*frontRef = source;
*backRef = NULL;
}
else
{
slow = source;
fast = source->next;
/* Advance 'fast' two nodes, and advance 'slow' one node */
while (fast != NULL)
{
fast = fast->next;
if (fast != NULL)
{
slow = slow->next;
fast = fast->next;
}
}
/* 'slow' is before the midpoint in the list, so split it in two
at that point. */
*frontRef = source;
*backRef = slow->next;
slow->next = NULL;
}
}
void printList(struct node *node)
{
while(node!=NULL)
{
printf("%d ", node->data);
node = node->next;
}
}
/* Function to insert a node at the beginging of the linked list */
void push(struct node** head_ref, int new_data)
{
/* allocate node */
struct node* new_node =
(struct node*) malloc(sizeof(struct node));
/* put in the data */
new_node->data = new_data;
/* link the old list off the new node */
new_node->next = (*head_ref);
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* Drier program to test above functions*/
int main()
{
/* Start with the empty list */
struct node* res = NULL;
struct node* a = NULL;
/* Let us create a unsorted linked lists to test the functions
Created lists shall be a: 2->3->20->5->10->15 */
push(&a, 15);
push(&a, 10);
push(&a, 5);
push(&a, 20);
push(&a, 3);
push(&a, 2);
/* Sort the above created Linked List */
MergeSort(&a);
printf("\n Sorted Linked List is: \n");
printList(a);
getchar();
return 0;
}