Need advise

[krakatao]

Hello! I will write program in which you should enter 20 or more real numbers write them into .dat file and program should read from that .dat file and sort first 20 numbers, also sum all the number. I need advise or maybe if you have some example what is the bet way to do it because i tried few methods but **** happens.

[laserlight]

What is your best attempt?

[krakatao]

I only started to write into file and read what i wrote but i am getting 0,000000 instead of number i entered so i can't do following actions :/

#include <stdio.h>
#include <stdlib.h>


int main()
{
FILE *fp;
int i=1;
char numbers[200];
   
    
if ( (fp=fopen("numbers.dat","wb+"))==NULL)
{
     printf ("No such file \n");
     system("pause");
     exit(1);
}
printf ("Enter number \n");
printf ("End of input ctrl+z \n");

while (!feof(stdin))
{
      printf("Enter %d  number : \n",i);
      fscanf(stdin,"%f",&numbers[i]);
      fseek( fp, i *  sizeof( float ), SEEK_SET );
      fwrite(&numbers[i], sizeof(float),1,fp);
      i++;
}
i=0;
rewind(fp);
printf("Number you entered : \n");
while (!feof(fp))
{
      fread(&numbers[i], sizeof(float),1,fp);
      printf("%f ", numbers[i]);
      i++;
}
system("pause");
}

P.S. It works only with integer but not with float

[oogabooga]

Your main problem is that you've defined numbers as a char array whereas if it's going to hold floats it should be of type ... float.

Also, your loop control is not correct. Try something like this (and note that you don't need the fseek since the file pointer will automatically advance after each fwrite).

while (1) {
      printf("Enter %d  number : \n",i);
      if (fscanf(stdin, "%f", &numbers[i]) != 1)
          break;
      fwrite(&numbers[i], sizeof(float), 1, fp); // should actually check return value here too!
      i++;
}
i=0;
rewind(fp);
printf("Number you entered : \n");
while (1) {
      if (fread(&numbers[i], sizeof(float), 1, fp) != 1)
          break;
      printf("%f\n", numbers[i]);
      i++;
}

[krakatao]

Thank you. One more question. If there is possibility in this case to sort numbers without storing them into array?

[laserlight]

If there is possibility in this case to sort numbers without storing them into array?

You need to store them somewhere to sort them. Like, if I read out a list of numbers to you and ask you to sort them, you won't be able to do so if you forget each number as soon as I read the next one to you.

[krakatao]

Yes i understand. I mean not storing all file into array. Just those elements which i need to compare

[krakatao]

Still cannot find a way to sort first 20 numbers. I tried something like this :/

#include <stdio.h>
#include <stdlib.h>

int main()
{
FILE *fp;
int i=1,k,j;
float numbers,average=0,now,temp,minimum;

   
    
if ( (fp=fopen("numbers.dat","wb+"))==NULL)
{
     printf ("No such a file \n");
     system("pause");
     exit(1);
}
printf ("Enter number\n");
printf ("End ctrl+z \n");

while (!feof(stdin))
{
      
      printf("Enter %d number : \n",i);
      fscanf(stdin, "%f", &numbers);
      if(feof(stdin))
      {
      break;
      }
      fwrite(&numbers, sizeof(float),1,fp);
      i++;
}
i=0;
rewind(fp);
printf("Numbers you entered : \n");
while (1)
{
      if (fread(&numbers, sizeof(float), 1, fp) != 1)
      break;
      printf("%f ", numbers);
      average=average+numbers;
      i++;
}
average=average/i;
system("pause");
rewind(fp);
/*SORTING*/
for (j=1; j<=20; j++)
{
minimum=fread(&numbers, sizeof(float), 1, fp);
for (k=j; k<=20; k++)
{
    now=fread(&numbers, sizeof(float), 1, fp);
    if (now<minimum)
    {
    temp=0;
    temp=minimum;
    minimum=now;
    fseek(fp,j*sizeof(float),SEEK_SET);
    fwrite(&minimum, sizeof(float),1,fp);
    }
}
    fseek(fp,k*sizeof(float),SEEK_SET);
    fwrite(&temp, sizeof(float),1,fp);
    
}
/*SORTING*/
rewind(fp);
while (1)
{
      if (fread(&numbers, sizeof(float), 1, fp) != 1)
      break;
      printf("%f ", numbers);
}
system("pause");         


}

[MK27]

There are a number of well known, common sorting algorithms:

Sorting algorithm - Wikipedia, the free encyclopedia

The first three are probably the simplest. Insertion sort might apply best to what you are doing, because it involves reading in one number at a time and inserting it into an array.

Pick one, try to implement it, and if it doesn't work out, you can say, eg, "What's wrong with my bubblesort?".

[krakatao]

There are a number of well known, common sorting algorithms:

Sorting algorithm - Wikipedia, the free encyclopedia

The first three are probably the simplest. Insertion sort might apply best to what you are doing, because it involves reading in one number at a time and inserting it into an array.

Pick one, try to implement it, and if it doesn't work out, you can say, eg, "What's wrong with my bubblesort?".

The problem is i can't print out floats from array(it prints out smiles instead of numbers).

[laserlight]

The problem is i can't print out floats from array(it prints out smiles instead of numbers).

Well, what line of code did you use to "print out floats from array". Also, show the declaration of the array.

[krakatao]

Well, what line of code did you use to "print out floats from array". Also, show the declaration of the array.

array[0]=fread(&numbers, sizeof(float), 1, fp);
printf("%s \n",array);
system("pause");
}

[laserlight]

What is array?

[krakatao]

char array[200];

[krakatao]

What is array?

char array[200];