我应该怎么做才能使链表中的最后一个节点参与冒泡排序？

Question

I have written a linked list program and I ought to program a bubble sorting function, but the last node seems to not participate in the bubble sort. I guess that's because the pointer moves to NULL and rejects the last node data. Can you please suggest me a way to sort the linked list in any other way, that would also help.

My code is:

#include<stdio.h>
#include<stdlib.h>
typedef struct node_type{
   int data;
   struct node_type *next;
}node;

typedef node *list;
list head;

void traverse()
{
   list temp;
   temp=head;
   printf("\nThe Data is: \n");
   while(temp!=NULL)
   {
      printf("%d\n",temp->data);
      temp=temp->next;
   }
   printf("\n\n");
}

void sort_list()
{
   list new,ptr;
   int temp;
   for(new=head;new->next!=NULL;new=new->next)
   {
       for(ptr=new->next;ptr->next!=NULL;ptr=ptr->next)
       {
           if(new->data > ptr->data)
              {
                  temp=new->data;
                  new->data=ptr->data;
                  ptr->data=temp;
              }  
        }
   }
   traverse();
   }

void main()
      {
         list temp,new;
         head=NULL;
         int n;
         char ch;
         temp=(list) malloc(sizeof(node));
         printf("\nGive data: ");
         scanf("%d",&temp->data);
         head=temp;
         printf("\n");
         printf("Enter more data(y/n): ");
         scanf("\n%c",&ch);
         while(ch=='y')
            {
               new=(list) malloc(sizeof(node));
               printf("Give data: ");
               scanf("%d",&new->data);
               temp->next=new;
               temp=new;
               printf("\nEnter more data(y/n): ");
               scanf("\n%c",&ch);
            }
       temp->next=NULL;
       traverse(head);
       printf("\n\nDo you want to sort the Link-List(y/n): ");
       scanf("\n%c",&ch);
       if(ch=='y')
          { 
             sort_list();
          }
    }

Input: 2 3 1 5 4

Output: 1 2 3 5 4

Answer 1

The inner loop of sort_list() is not considering the last node during sorting because of the condition ptr->next!=NULL in for loop. You should check it ptr with NULL :

for(ptr = new->next; ptr != NULL; ptr = ptr->next)
                     ^^^^

Answer 2

There are several things that needs to be fixed.

• The main function needs to have a return value of int not void .
• There are calls to traverse that pass head as an argument, which will give an error. Either update the traverse function to except a list argument, or fix those calls.

• The sort_list function's inner for loop's condition should end when ptr == NULL ie

   for(ptr=new->next; ptr != NULL; ptr=ptr->next) 

The function could be more defensive, if head happens to be NULL , the first for loop would cause a segmentation fault when new->next != NULL becomes evaluated. You could have an if statement at the beginning of the function to guard against this.

• The last thing is since malloc is being used, make sure that memory is freed. You will need to iterate through the list and free each node.