Thread: Swap two nodes in linked list

I want to swap two nodes of a linked list. Like if its 12 23 34 45 then i want result like 21 32 43 54..... if input is 12345 then output should be 21435. something like that...


I have written following .... but its not producing the desired output ..... somebody plz help me out

#include<stdio.h>
#include<conio.h>
#include<malloc.h>


struct list{
int roll_no; /* Storing roll number of a node */
// char name[N]; /* Storing name of node */
float marks; /* Storing marks of a node */
struct list *next; /* Storing next address */
};
/***** Redefining struct list as node *****/
typedef struct list node;
node* swap(node *current)
{
int rno; /* Roll number for swaping node*/
int t; /* Total number of nodes */
node *temp; /* Temporary copy of current */
node *tmp; /* Temporary variable */
t=number(current);
if(t<=1)
{
printf("\nYou cannot swap the only node\n");
return(current);
}
printf("\nEnter roll number whose node you want to swap with the next\n");
scanf("&#37;d",&rno);
temp=current;
if(current->roll_no==rno)
{
tmp=current->next;
current->next=current->next->next;
tmp->next=current;
current=tmp;
return(current);
}
else
{
while(temp->next->next!=NULL)
{
if(temp->next->roll_no==rno)
{
tmp=temp->next->next;
temp->next->next=temp->next->next->next;
tmp->next=temp->next;
temp->next=tmp;
break;
}
temp=temp->next;
}
return(current);
}
}

int main()
{
head=swap(head); // head is the first node of the linked list
getch();
}

so you want to reverse the integers? give a search here or elsewhere as im sure its been covered before. if you dont want to search and want specific help, then please post an attempt at reversing a number. once you have done that im sure your help will come.

edit: after rereading, it looks like your first example just involved reversing each integer in a list. the second example is a different case in which one number is entered and the digits are switched. so it looks like two problems.

the first one i talked about above, the second one, a starting point would be to determine if the length of the integer is odd or even, as since 12345 has an odd number of numbers, only the first 4 are switched, however if it were 1234 it should switch to 2143 in which case all the numbers are switched. i would grab some paper, draw out 12345 and think of the steps to get it to become 21435, writing out every single step (as you know a computer would have to be told). once you have that, do it again for a number 1234, as this is the second case.

this doesnt really have anything to do with a linked list, so im sure im misunderstanding.

And investigate the [code] tags!

QuantumPete