Doubly linked list crashing after trying to print from end
It crashes after choosing option 3.
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
|
#include <iostream>
using namespace std;
struct node{
int data;
struct node *next;
struct node *prev;
};
void create_list(int num);
void display_dlist();
void reverse_display_dlist();
struct node *head = NULL;
int main()
{
int choice, value, position;
while (1){
cout<<endl<<"----------------------------"<<endl;
cout<<endl<<"Operations on Doubly linked list"<<endl;
cout<<endl<<"----------------------------"<<endl;
cout<<"1.Create doubly linked list"<<endl;
cout<<"2.Print from start"<<endl;
cout<<"3.Print from end"<<endl;
cin>>choice;
switch (choice){
case 1:
cout<<"Enter value: ";
cin>>value;
create_list(value);
cout<<endl;
break;
case 2:
display_dlist();
break;
case 3:
reverse_display_dlist();
break;
default:
cout<<"Option doesnt exist"<<endl;
break;
}
}
return 0;
}
void create_list(int num){
struct node *temp, *temp1;
temp = new node;
temp->data = num;
temp->next = NULL;
if(head == NULL){
temp->prev = NULL;
head = temp;
}
else{
temp1 = head;
while(temp1->next != NULL)
temp1 = temp1->next;
temp1->next = temp;
temp->prev = temp1;
}
}
void display_dlist(){
struct node *temp = head;
while(temp != NULL){
cout<<temp->data<<" ";
temp = temp->next;
}
cout<<endl;
}
void reverse_display_dlist(){
struct node *temp = head;
while(temp != NULL){
temp = temp->next;
}
do{
cout<<temp->data<<" ";
temp = temp->prev;
}while(temp != head);
cout<<endl;
}
|
Time to learn about debuggers.
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
|
$ g++ -Wall -Wextra -g foo.cpp
foo.cpp: In function ‘int main()’:
foo.cpp:19:24: warning: unused variable ‘position’ [-Wunused-variable]
int choice, value, position;
^
$ gdb -q ./a.out
Reading symbols from ./a.out...done.
(gdb) run
Starting program: /home/sc/Documents/a.out
Operations on Doubly linked list
1.Create doubly linked list
2.Print from start
3.Print from end
1
Enter value: 22
Operations on Doubly linked list
1.Create doubly linked list
2.Print from start
3.Print from end
3
Program received signal SIGSEGV, Segmentation fault.
0x0000000000400bf3 in reverse_display_dlist () at foo.cpp:88
88 cout<<temp->data<<" ";
(gdb) p temp
$1 = (node *) 0x0
(gdb) list
83 struct node *temp = head;
84 while(temp != NULL){
85 temp = temp->next;
86 }
87 do{
88 cout<<temp->data<<" ";
89 temp = temp->prev;
90 }while(temp != head);
91
92 cout<<endl;
(gdb)
|
Your first while loop needs to stop at the last node, not fall off the end.
Last edited on
Thanks for your help.
Here's the working code:
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
|
#include <iostream>
using namespace std;
struct node{
int data;
struct node *next;
struct node *prev;
};
void create_list(int num);
void display_dlist();
void reverse_display_dlist();
node *head = NULL;
node *tail= NULL;
int main()
{
int choice, value, position;
node *head = NULL;
node *tail= NULL;
while (1){
cout<<endl<<"----------------------------"<<endl;
cout<<endl<<"Operations on Doubly linked list"<<endl;
cout<<endl<<"----------------------------"<<endl;
cout<<"1.Create doubly linked list"<<endl;
cout<<"2.Print from start"<<endl;
cout<<"3.Print from end"<<endl;
cin>>choice;
switch (choice){
case 1:
cout<<"Enter value: ";
cin>>value;
create_list(value);
cout<<endl;
break;
case 2:
display_dlist();
break;
case 3:
reverse_display_dlist();
break;
default:
cout<<"Option doesnt exist"<<endl;
break;
}
}
return 0;
}
void create_list(int num){
struct node *temp, *temp1;
temp = new node;
temp->data = num;
temp->next = NULL;
if(head == NULL){
temp->prev = NULL;
head = temp;
}
else{
temp1 = head;
while(temp1->next != NULL)
temp1 = temp1->next;
temp1->next = temp;
temp->prev = temp1;
tail = temp;
}
}
void display_dlist(){
struct node *temp = head;
while(temp != NULL){
cout<<temp->data<<" ";
temp = temp->next;
}
cout<<endl;
}
void reverse_display_dlist(){
struct node *temp = tail;
do{
cout<<temp->data<<" ";
temp = temp->prev;
}while(temp != head);
temp = head;
cout<<temp->data;
cout<<endl;
}
|
Better.
Now do it without using any global variables.
Okay, I will try.
Would it be hard to remove global variables later?
I want to finish the whole program using my method first.
Topic archived. No new replies allowed.