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
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
|
/*
* C++ Program to Implement Merge Sort using Linked List
*/
#include <iostream>
#include <cstdio>
#include <string>
#include <cstdlib>
#include <fstream>
using namespace std;
/*
* Node Declaration
*/
struct node
{
string data;
int num;
struct node* next;
};
struct node* SortedMerge(node* a, node* b);
void FrontBackSplit(node* source, node** frontRef, node** backRef);
/* sorts the linked list by changing next pointers (not data) */
void MergeSort(struct node** headRef)
{
node* head = *headRef;
node* a;
node* b;
if ((head == NULL) || (head->next == NULL))
{
return;
}
FrontBackSplit(head, &a, &b);
MergeSort(&a);
MergeSort(&b);
*headRef = SortedMerge(a, b);
}
/* merge the sorted linked lists */
node* SortedMerge(struct node* a, struct node* b)
{
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;
}
/* Split the nodes of the given list into front and back halves*/
void FrontBackSplit(node* source, node** frontRef, node** backRef)
{
node* fast;
node* slow;
if (source==NULL || source->next==NULL)
{
*frontRef = source;
*backRef = NULL;
}
else
{
slow = source;
fast = source->next;
while (fast != NULL)
{
fast = fast->next;
if (fast != NULL)
{
slow = slow->next;
fast = fast->next;
}
}
*frontRef = source;
*backRef = slow->next;
slow->next = NULL;
}
}
/* print nodes in a given linked list */
void printList(node *node)
{
while (node != NULL)
{
cout<<node->data<<endl;
node = node->next;
}
}
/* insert a node at the beginging of the linked list */
void push(node** head_ref, string new_data)
{
node *new_node = new node;
new_node->data = new_data;
new_node->next = (*head_ref);
(*head_ref) = new_node;
}
/* Main */
int main()
{
int num;
string file_name;
string file;
ifstream infile;
node* res = NULL;
node* a = NULL;
cout << "What file would you like to open: ";
getline(cin, file_name);
infile.open(file_name);
while(infile >> num && (getline(infile, file)))
{
push(&a, file);
}
MergeSort(&a);
cout<<"\n Sorted Linked List is: \n";
printList(a);
system("Pause");
return 0;
}
|
