strncmp in Linked List

Question

This program should allow the user to input some names (until the user wishes to continue.) and then display those names in ascending order. I have used the strncmp function in comparing the char arrays. But when this is run, only the 1st and last name of the sorted name list is given as the output (which means, the list was sorted). But I cannot find out why the names in between them aren't displayed. Please help me! Thank you.

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

char name[10];
int place;

struct node
{
  char nm[10];
  struct node *next;
}*newnode, *prev, *temp, *display, *current, *list;

void createlist()
{
  list = NULL;
}
;

void insert()
{
  newnode = (struct node*) malloc(sizeof(struct node));

  printf("Enter the Name: ");
  scanf("%s", &name);
  strncpy(newnode->nm, name, 10);
  newnode->next = NULL;

  if (list == NULL )
  {
    list = newnode;
  }
  else if (strncmp(name, list->nm, 10) < 0)
  {
    newnode->next = list;
    list = newnode;
  }
  else
  {
    temp = list;

    place = 0;

    while (temp != NULL && place == 0)
    {
      if (strncmp(name, temp->nm, 10) >= 0)
      {
        prev = temp;
        temp = temp->next;
      }
      else
      {
        place = 1;
      }
      newnode->next = prev->next;
      prev->next = newnode;
    }
  }
}

void displayname()
{
  if (list == NULL )
    printf("\n\nList is empty");
  else
  {
    display = list;
    while (display != NULL )
    {
      printf("%s\n", display->nm);
      display = display->next;
    }
  }
}

int main()
{

  char choice;
  choice == 'y';

  createlist();
  do
  {
    insert();
    printf("Do you want to continue? ");
    scanf("%s", &choice);
  } while (choice = 'y' && choice != 'n');

  displayname();
}

It doesn't necessarily mean the list was sorted. It may mean the list was corrupted. — n. m. could be an AI, Sep 08 '13 at 09:02
The best way to learn is to step through your program by using a debugger. However: do not cast `malloc`. — pzaenger, Sep 08 '13 at 09:06

surender8388 · Answer 1 · 2013-09-09T09:49:00.513

In your insert function, you are useing

newnode->next = prev->next;
prev->next = newnode;

use like

newnode->next = temp;
prev->next = newnode;

[EDIT]

Use your insert function like this.

void insert()
{
    newnode = (struct node*) malloc(sizeof(struct node));

    printf("Enter the Name: ");
    scanf("%s", &name);
    strncpy(newnode->nm, name, 10);
    newnode->next = NULL;

    if (list == NULL )
    {
        list = newnode;
    }
    else if (strncmp(name, list->nm, 10) < 0)
    {
        newnode->next = list;
        list = newnode;
    }
    else
    {
        temp = list;

        prev = NULL;
        // prev is a global variable, So assign it to NULL each time, Otherwise it will keep old value.
        while (temp != NULL)
        {
            if (strcmp(name, temp->nm) >= 0)
            {
                prev = temp;
                temp = temp->next;
            }
            else
            {
              break;

            }
        }
        newnode->next = temp;
        prev->next = newnode;
    }
}

Now do remember one thing, In your code,

in main() your are doing

choice == 'y'; that is not assignment. You should use

choice = 'y';
in your main(), in do{}while() your are using

while (choice = 'y' && choice != 'n'); choice ='y' is assignment, not comparison. use like this

while (choice == 'y' && choice != 'n');
in main(), you are using

scanf("%s", &choice); // choice is a char, you are trying to have string (%s) here. That will memory corruption So use it like this,

choice = getche();

I put almost whole code in [EDIT] and mentioned some points to take care. Still you find any issues, let me know. — surender8388, Sep 09 '13 at 09:51

score 0 · Answer 2 · answered Sep 09 '13 at 06:35

change your else in the insert function to the following:

else
{
    temp = list;
    while(temp !=NULL && strncmp(temp->nm,name,10)<0)
    {
        prev=temp;
        temp=temp->next;
    }
    if(temp==NULL)
        prev->next=newnode;
    else
    {
        newnode->next=temp;
        prev->next=newnode;
    }

}

strncmp in Linked List

2 Answers2