Reading (and printing) the frequency of an integer in another file

Question

I have to read text in from a file, then prompt for a value and search the file for this number. Once the file is read all the way through, I have to print the initial position and the number of times it appears. Obviously I do not just want the answer, but rather where my program went wrong because I am blind to it as of now.

My source code looks like this:

    int count, number, value;
    printf("What number are you looking for? ");
    scanf("%d",&value);

    FILE *fp = fopen("data.in","r");
    count = 0;
    while (!feof(fp)) {
        fscanf(fp,"%d",&number);
        if (number == value) {
            ++count;
            }
        }
    fclose(fp);

    printf("The number %d appears first at position %d in the file",value,number);
    printf("The number %d appears %d time(s)",value,count);

    return 0;
}

The data file I am reading from is:

3 8 33 75 25 10 41 8
10
 55 10 1 0 10
10 18

However, when I run the program it returns:

What number are you looking for? 10

The number 10 appears first at position 18 in the file

The number 10 appears 5 time(s)


What number are you looking for? -5

The number -5 appears first at position 18 in the file

The number -5 appears 0 time(s)

Any ideas? Again, I am not looking for the straight answer, rather a way for me to look for these issues both now and in the future.

You're not keeping track of the position of where the desired number was first seen (you're displaying a value from the file instead). You need to record that position the first time you see the desired number. — nobody, Mar 08 '15 at 16:14
`while(!feof(fp))` is wrong. Replace `!feof(fp)` with the `fscanf` along with `==1` — Spikatrix, Mar 08 '15 at 16:15

score 3 · Answer 1 · edited May 23 '17 at 12:20

3

After coming out from while loop number is always the last number i.e. 18 irrespective of number you are looking for.

The line fscanf(fp,"%d",&number); reads the number of each line and when loop terminates the number is assigned as 18.

^{Also read : “while( !feof( file ) )” is always wrong ?}

Do something like following:

int pos = -1, curr_lno = 0 ; // Keep track of position
while (fscanf(fp,"%d",&number) == 1) 
{
    ++curr_lno ;
    if (number == value) 
    {
        pos = ( pos == -1 ) ? curr_lno : pos ;
        ++count;
    }
}
fclose(fp);

if ( count > 0 )
{
    printf("The number %d appears first at position %d in the file",value, pos );
}

edited May 23 '17 at 12:20

Community

1
1

answered Mar 08 '15 at 16:12

P0W

46,614
9
72
119

You'll get position 15 instead of 6 if you entered 10 as input.`"The number %d appears **first** at position %d in the file"`. – Spikatrix Mar 08 '15 at 16:22
@CoolGuy Sorry didn't notice that, fixed now. There can be easy way out though, left as an assignment for OP :D – P0W Mar 08 '15 at 16:29
Okay so I see where I went wrong with the initial and took a slightly path but with your guideline I figured it out!! Thank you so much!!! – yup Mar 08 '15 at 16:50

Reading (and printing) the frequency of an integer in another file

1 Answers1