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i have a file which lists people.
each person is either
type 0 or type 1 people
and each person has an ID.
each line in the file represents a person.
the file is not sorted in any way not by id nor by type.
how to take the data from that file
so i will create two files sorted by ID and each file has people with the same type
??
Its easy, read the list from the file and store them in a struct array. Sort the structure array with the ID and write them onto the file and then sort the structure array with the other attribute and write them onto a different file.
-ssharish
i am not allowed to rewind.
only to read the file once
They didn't mention using rewind. Seriously, you need to start putting some thought into your problems instead of just posting them here for us to do them all for you. We're not here to teach you basic logic, or to do your homework.
Quzah.
i am not allowed to copy the whole file in to a struct .
define rewind.
ssharish is saying that you read the file into an array in memory, sort the array, and write out the elements to two separate files.
i am looking for some way that as i go by each line
then it sorts in the write place in it designated file.
Ohh well, show us how your file looks like?
-ssharish
i am not allowed to read the whole file into a data structure.
Well, you cant do that. You can at the most do one task at a time. Not reading and writing at the same time. The file will be locked to do anything else.Quote:
Originally Posted by transgalactic2
Well, not excatly you can. But position the file pointer is the biug problem.
-ssharish
each line in that file represents a person
in each line i have ID 9 chars
and type (0 or 1) 1 char
and i have a list of many people
mixed up
i ment writing the line from the mixed fileQuote:
Originally Posted by ssharish2005
into the sorted file which it belongs to by its type.
Fine! have you written any code so far? Can you show us what you have got so far? Have you tried reading a file?
-ssharish
yes i have built a helping function which gets an ID
and finds the smallest ID amongst the other which is bigger then the intput
for example:
if the input is 4 and the list is
7
8
6
then it returns 6
this is the whole code
including the start of the function i want to build
void balance(FILE * Room1, FILE * Room2, char* course1,char* course2);
Code:#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct line {
char name[21], address[21];
int grade, ID;
int code;
};
void balance(FILE * Room1, FILE * Room2, char* course1,char* course2);
struct line next_Id(FILE * room , int last_ID);
int main ()
{
FILE* c[2];
struct line temp;
c[0]=fopen("c:\\fl1.txt","r");//vote files ,each file represents the votes from a college
c[1]=fopen("c:\\fl2.txt","r");
temp=next_Id(c[0] , 666666666);
fclose(c[0]);
fclose(c[1]);
return 0;
}
struct line next_Id(FILE * room , int last_ID)
{
struct line temp,min,tmin;
int flag;
do
{
flag=fscanf(room,"%10s%10s%10d%10d%10d%*c",&temp.name,&temp.address,&temp.ID,&temp.grade,&temp.code);
}while(temp.ID<last_ID);
do
{
flag=fscanf(room,"%10s%10s%10d%10d%10d%*c",&min.name,&min.address,&min.ID,&min.grade,&min.code);
if ((min.ID>last_ID)&&(min.ID<temp.ID)&&(flag==5))
{
tmin=min;
}
else
{
if(flag==5)
tmin=temp;
}
}while (flag==5);
return tmin;
}
void balance(FILE * Room1, FILE * Room2, char* course1,char* course2)
{
struct line temp[2];
int flag[2];
temp[0]=next_Id(Room1,000000000);
flag[0]=fscanf(Room1,"%10s%10s%10d%10d%10d%*c",&temp[0].name,&temp[0].address,&temp[0].ID,&temp[0].grade,&temp[0].code);
//flag[1]=fscanf(Room2,"%10s%10s%10d%10d%10d%*c",&temp[1].name,&temp[1].address,&temp[1].ID,&temp[1].grade,&temp[1].code);
while()
{
}
}
There.Code:while read line from file doesn't produce EOF
append to odd ? odd file : even
sort odd file
sort even file
Quzah.
"sort odd file
sort even file"
i cant read files more then once??
" append to odd ? odd file : even"
what this means?
i know the ? : form
what you mean here?
Ohh man, you really need help. He gave a whole lot of hints
I am waiting for Quzah's comments
-ssharish
You don't have to read a file to append to it. Therefore, since you can only read each file once:
1 - Open the mixed file for reading.
2 - Open output.odd in append mode.
3 - Open output.even in append mode.
4 - Read the input file, appending as you go to the appropriate file.
5 - Close the input all the files.
6 - Open one of the output files for reading/writing.
7 - Read it into memory and sort it.
8 - Write it.
10 - Do steps 6 through 8 for the other output file.
There. Each file has been read only one time.
Quzah.
i am not allowed to use append
only "r" for the input
and "w" for the two output files
I doubt that. You aren't telling us the full requirements. How about in the future you actually tell us what the requirements of your homework are, since we're doing all the work here anyway. That way it will save us all a bunch of time.
You cannot perform this task in the manner you describe. Without being able to sort the data in memory, and with only being able to open in write mode, and with only being able to read through the input file once, and limiting yourself to two output files, you cannot do this task as you've described.
You're either not understanding the question, or are making stuff up because you don't like the answers you were given. If you cannot sort the file on disk, then you MUST sort it in memory. That's all there is to it. You either read through the file a bunch of times, or you read it once and sort it in memory. Pick one.
Quzah.
ok ill try to implement your solution.
nut i cant understand what append mode does.
i read in the manual of c++ that its "writing from the end"
so its moving the EOF forward and replacing the empty new space with the new data??
Append mode works just like write mode, with the difference that it does a fseek(file, 0, SEEK_END) - that is, it positiions the "where to access the file next" at the end of the file, so when you write to it, it adds to the end of the file, rather than writing at the first location of the file.Quote:
Originally Posted by transgalactic2
--
Mats
can you see a solution which uses
my helping function??
i am supposed to use it in the solution somehow
?
is there a way?
I've already told you, you are either going to have to read your file(s) more than once, or you're going to have to sort the entire thing in memory.
Quzah.