c program to read a text file and sort the information.

[priyanka raj]

Would you please help me in writing a c code to read data from a file and perform 1)numeric sort, 2)alphabetical sort.
the file may contain data of any kind.Like it may contain only numbers,only names or a database of employees of a company.(which contains their employee id,name,designation and salary,....in different fields).Each line contains details of one employee.
Sorting has to be done based on field specified.i.e,if sorting has to be done considering 3rd field(designation),
alphabetical sort has to be performed.And if the specified field contains information other than name or designation numeric sort has to be performed.
I would prefer a c program to solve the above problem.

[ahmedhamdy]

you make struct Employee has(id ,name,salary,....) and make every Employee as node in linked list
then
save linked list into file after fill some data

then
read data from file and you can sort data by bubble sort :
(if you need numeric sort then sort nodes by id )
or
(if you need alphabetical sort then sort nodes by name)

[ahmedhamdy]

data for one Employee you need read from file ,has already in file or not?

[priyanka raj]

Thank you.I tried sorting numerically.it worked.But alphabetical sort(i.e sorting based on names) is giving trouble.Can u please give the logic or the code for sorting "emp->name" field in my linked list.

[deceptikon]

The logic for sorting with string keys is no different than with numeric keys. The only difference is in the comparison, where with string keys you cannot use relational operators. Instead, compare with strcmp():

if (strcmp(a->name, b->name) < 0) {
    /* a->name is lexicographically smaller than b->name */
    ...
}

This is as opposed to the numeric way of just comparing directly:

if (a->id < b->id) {
    /* a->id is numerically smaller than b->id */
    ...
}

Other than that, your sorting algorithm shouldn't change unless you also move around the data (in which case some variation of strcpy() may be needed). But since you're already storing these records in structures, you can just copy the structure instances and all will be well.

[ahmedhamdy]

deceptikon has solved the problem of sorting data by name

[ahmedhamdy]

struct data  \\\<<<  data for every node 
{
char name[20];
int id;
};

struct node    \\\<<<  node for linked list
{
struct data;
struct node*prev;
struct node*next;
};

struct node*head;
struct node*tail;

void bubble_sort()  \\\<<< sorting  nodes by bubble sort
{ 
int i,j,size;
struct Node*current;
struct Node*temp;
     size=0;
     PCurrent=PHead;

     while(current)
       {
          current=current->Next;
            size++;         
        }

PCurrent=PHead; 

for(i=0;i<size;i++)
{
    for(j=0;j<size-i;j++)
    {

        if(strcmp(current->next->data.name,current->data.name)<0)  \\\<<< sorting alaphabetic
        {


                temp->data=current->data;
                current->data=current->next->data;
                current->next->data=temp->data;                      


        }
        else if(current->next->data.id>current->next->data.id)   \\\<<< sorting  nomarical
        {

                temp->data=current->data;
                current->data=current->next->data;
                current->next->data=temp->data; 

        }                 
    current=current->Next;

     }
 current=head;  


 }             




}

[ahmedhamdy]

strcmp in string.h library

[ahmedhamdy]

sorry you must declare struct node*current as public

current pointer used to point for current node which you stop on it

[priyanka raj]

Guys thank you so much.I did get my programming working. But i dropped the idea of using linked list.instead, i used a two dimensional character array and stored the items scanned from the file opened in read i.e "r" mode in that char array. And then,i've sorted them using strcmp funtion using bubble sort method.
Thanks again guys.I didn't expect anyone to even bother about my question,but i'm happy now.

[priyanka raj]

Guys thank you so much.I did get my programming working. But i dropped the idea of using linked list.instead, i used a two dimensional character array and stored the items scanned from the file opened in read i.e "r" mode in that char array. And then,i've sorted them using strcmp funtion using bubble sort method.
Thanks again guys.I didn't expect anyone to even bother about my question,but i'm happy now.

[aaaymen]

What's the role of "PCurrent=PHead; " (line31)?