Learning arrays

Unregistered · 07-09-2002

I'm writing a program to read numbers from a file and then print out the largest and second largest numbers in that file.
What am I doing wrong? Thanks for the help.
#include <stdio.h>
#include <stdlib.h>
#define SIZE 50

int main()
{

int values[SIZE],
largest,
second_largest,
newest;
int count = 0;
int i;
FILE *input_file_ptr;
input_file_ptr = fopen("data.c","r");
if (input_file_ptr == NULL)
{
printf("The data file couldn't be opened.\n");
return 0;
}
else /*read the file into the array*/
{
while (fscanf(input_file_ptr;"%d", &newest)==1)
{
values[count] = newest;
count++;
}
}
/*search for the largest element*/

switch(count)
{
case 0: printf("No largest or second largest.");
break;
case 1: printf("The largest number is %d.\n",values[0]);
printf("There is not a second largest.\n");
break;

case 2: if (values[0]< values[1])
{
printf("Largest is %d, second largest is %d.",
values[1],values[0]);
break;
}
else (values[0]> values[1])
{
printf("Largest is %d, second largest is %d.",
values[0],values[1]);
break;
}

default: break;/*cases larger than 2*/
}

largest = values[0];
second_largest = values[0];

for (i=1; i < 50; i++)
{
{ if (values[i]>largest)
largest = values[i];
else if (values[i]== largest)
largest = second_largest;
else if (values[i]> second_largest)
second_largest = values[i];
}

if (largest == second_largest)
{
printf("The largest and second largest are the same");
printf(" number: %d.\n",largest);
}
else if (largest != second_largest)
{
printf("The largest number is: %d.\n",largest);
printf("The second largest number is: %d.\n",second_largest);
}
}
return 0;

}

**Prelude** · 07-09-2002

Your two bugs are here:
>while (fscanf(input_file_ptr;"%d", &newest)==1)

And here:
>else (values[0]> values[1])

The first bug is easily fixed by changing the semicolon after input_file_ptr to a comma and the second by either removing the test or changing the else to an else if.

Personally, I think you're making this way too complicated. Just keep two survivor variables and at the end of the program, they will contain the largest and second largest values:

Code:

#include <stdio.h>

int main ( void )
{
  int largest = 0,
      nextLargest = 0,
      rawVal;
  char buffer[BUFSIZ];
  printf ( "Enter a series of integers (CTRL+Z to quit)\n$ " );
  while ( fgets ( buffer, sizeof buffer, stdin ) != NULL ) {
    if ( sscanf ( buffer, "%d", &rawVal ) == 1 ) {
      if ( rawVal > largest ) {
        nextLargest = largest;
        largest = rawVal;
      }
      else if ( rawVal > nextLargest )
        nextLargest = rawVal;
    }
    else
      (void)puts ( "Invalid integer" );
    printf ( "$ " );
  }
  printf ( "The largest value is: %d\n"
           "The next largest is:  %d\n", largest, nextLargest );
  return 0;
}

This can easily be converted to read from a file instead of standard input.

-Prelude

**foniks munkee** · 07-09-2002

What is the error that you are getting?

I can see that you have put a semi colon after the first argument to fscanf. This should be a comma - so your code wont compile right there.

Code:

while (fscanf(input_file_ptr;"%d", &newest)==1)

And.. the else should be an "else if" if you wish to evaluate another statement. Making these changes should allow it to compile, I haven't actually checked the logic though.

Code:

else (values[0]> values[1])

Oh, I think there are a couple of unnecassary brackets in there as well - that may cause some compilation errors. I think one of them was in this block of code.

Code:

for (i=1; i < 50; i++) 
{ 
{ if (values[i]>largest) 
	  largest = values[i]; 
  else if (values[i]== largest) 
  	largest = second_largest; 
  else if (values[i]> second_largest) 
  	second_largest = values[i]; 
}

Also - please use the code tags when posting code, it makes it easier to read

**foniks munkee** · 07-09-2002

Ahh.. Damn - I think you can type faster than I can Prelude.

Unregistered · 07-09-2002

Thanks for the help guys. My logic is messed up but at least it is compiling now.

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