Problem with linked list "delete"
Jun 5, 2014 at 7:16am UTC
Hi everybody,
I am writing my first linked list , where till now I have done insert and print are working properly, delete is giving little problem.there are 3 cases .
1) if ther's only one node in the list and if we delete it then it gets deleted without any error but if I try to print after that it goes in an infinite loop.
2)suppose there are three nodes present and if the user deletes the first node of the list , it works fine and when I print after this it print also correct ,
3) If i want to delete some middle node like 2nd node, the output screen closes by itself
1 void link_list :: print_list()
{
if (head==NULL)
{
cout<< "Empty list" << endl;
}
else
{
int count = 0;
list=head;
while (list != NULL)
{
count++;
cout << "Node " << "value " << endl;
cout << count << " " << list->num << endl;
list = list->next;
}
}
}
void link_list :: del_pos()
{ //1
if (head==NULL)
{ //2
cout<<"List is empty can't delete" <<endl;
} //2
else
{ //3
char ch;
do
{ //4
node *s ;
int pos ;
int count =1;
s=head;
list=head;
cout<<"enter the node you wish to delete" <<endl;
cin >> pos;
if (pos==1 && head->next==NULL)
{ // 5
cout<<"u made the list empty !!!" <<endl;;
} //5
else
{ //6
if (pos==1)
{ //7
//s=head;
head=list->next;
} //7
else
{ //8
//s=list->next;
while (list!=NULL)
{ //9
list=list->next;
s=list->next->next;
count++;
if (count==pos)
{ //10
list->next = s->next;
break ;
} //10
}//9
} //8
} //6
delete s;
/* list=head;
while(list->next->!=NULL)
{
list=list->next;
}
list->next=NULL;*/
cout <<"do u wish to delete another node?" <<endl;
cin >> ch;
} while (ch=='y' ||ch=='Y' ); //4
} //3
}//1
Jun 5, 2014 at 7:53am UTC
1#include <stdexcept>
#include <string>
void link_list :: del_pos() {
char resp;
do {
if (this ->size() /*make a method called size*/ == 0) {
std::cout << "List is empty\n" ;
break ;
}
std::cout << "Enter a position to delete: " ;
unsigned pos;
std::cin >> pos;
if (pos < 1 || pos > this ->size() /*make a method called size*/ ) {
throw std::out_of_range("The value entered must be"
" between 1 and " + to_string(this ->size()));
}
for (node *currpos = head, *prev = nullptr ; --pos; prev = currpos, currpos = currpos->next)
;
if (prev == nullptr )
head = currpos->next;
else
prev->next = currpos->next;
delete currpos;
/*decrement size here*/
std::cout << "Do you wish to delete another node? " ;
std::cin >> resp;
} while (resp == 'Y' || resp == 'y' );
}
Last edited on Jun 5, 2014 at 7:54am UTC
Jun 5, 2014 at 9:33am UTC
thanks a lot for your reply , but at the same is it also possible to modify my code so that it runs perfectly ?
Jun 5, 2014 at 10:16am UTC
I have resoled the first problem by adding head=NULL; but still error 3 is there :( dont know how to do it, please help me.
Jun 5, 2014 at 12:41pm UTC
Someone please tell me me how to resolve the 3rd issue
Last edited on Jun 5, 2014 at 2:10pm UTC
Jun 5, 2014 at 1:20pm UTC
Where you have "head=NULL", Smac89 has lines 24-25.Smac89 has line 27.Smac89 's code does?
Jun 5, 2014 at 2:08pm UTC
I am sorry but I am not able to get my mistake
Jun 5, 2014 at 3:11pm UTC
1s = head; // s -> 0
list = head; // list -> 0
while ( list != NULL )
{
list = list->next; // list -> 1 (or NULL)
s = list->next->next; // s -> 3 (or NULL->next or NULL->next->next)
if (count==pos) // assume true
{
list->next = s->next; // 1.next == 4, i.e. positions 2 and 3 are forgotten
Jun 5, 2014 at 3:20pm UTC
I have modified the code a little bit , still getting the same error , console is stopping
1else
{ //6
if (pos==1)
{ //7
//s=head;
head=list->next;
} //7
else
{ //8
//s=list->next;
while (list!=NULL)
{ //9
list=list->next;
//s=list->next->next;
count++;
t=s;
s=list->next;
}//9
if (count==pos)
{ //10
t->next = s->next;
} //10
} //8
} //6
delete s;
cout <<"do u wish to delete another node?" <<endl;
cin >> ch;
} while (ch=='y' ||ch=='Y' ); //4
} //3
}//1
Jun 5, 2014 at 3:34pm UTC
even this is not working, what is wrong , someone please tell.
1else
{ //6
if (pos==1)
{ //7
//s=head;
head=list->next;
} //7
else
{ //8
//s=list->next;
while (list!=NULL)
{ //9
list=list->next;
//s=list->next->next;
count++;
}
if (count != pos)
{
t=list;
list=list->next;
}
else
{
t->next = list->next;
}
/*t=s;
s=list->next;
}//9
if(count==pos)
{ //10
t->next = s->next;
} //10*/
} //8
} //6
delete s;
cout <<"do u wish to delete another node?" <<endl;
cin >> ch;
} while (ch=='y' ||ch=='Y' ); //4
} //3
}//1
Jun 5, 2014 at 5:28pm UTC
Your indentation is not very informative (at least on the post).
Lets try something else for a moment. A simple excercise. Rewrite this Smac89's
for -loop as a
while -loop:
1for (node *currpos = head, *prev = nullptr ; --pos; prev = currpos, currpos = currpos->next)
;
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