Thread: getting 1000 chars at a time from stdin

ok.. im assured that the input will always be digits, and im not sure how to break out of both loops from the inner one. But my main problem is still there, when i enter a large number, the final digit isnt printed.

please help

Code:

#include <stdio.h>

#define maxSize 10001

int main (int argc , char** argv) {

	int counter = 0;
	char myArray[maxSize];
	
	do {

		if (fgets(myArray, maxSize, stdin) == NULL)
			break;
		
		for (counter=0; counter<maxSize; counter++) {
			
			if (myArray[counter] != '\n' && myArray[counter] != '\0') {
				printf("&#37;d", myArray[counter]-'0');
			}
			else
				break;
		}

	}
	while (myArray[counter] != '\n' && myArray[counter] != '\0');
	
	return 0;
}

Waxy, I believe you're focusing on the details here, rather than the right logic design.

I have another idea for this:

Use c=getchar (which actually returns to c an unsigned int), to get all the digits. If there's a million digits, that's OK, because after being checked that each one IS a digit, then they get written out to a file. The function isdigit() is made for this, btw.

10 million digits? You can take as many as your HD will have space for. And while you're taking in digits, you count how many you've taken in. When the count reaches 1000 ((number % 1000 == 0) && (number > 0)). then your program will write out an end of string char - '\0'.

When you get all the digits into the digits_in file, then close it.

Now re-open the digits_in file, and use fgets() to read in each of the 1000 digit strings, which will be no problem since you've put the end of string chars into the file.

(you could also just count them in from the file, digit by digit. No fun, but computers love that counting gig!).

You'll have substantial problem handling this logic, in "one pass", correctly. Nothing I've seen so far will do what you want. At best, they'll take in 1,000 digits and exit the program.

That's not what you said you wanted.

Adak

so if the number entered was 1000000.. etc there is no way to just get 1000 or even 500 digits at a time into a buffer until ive looped through them all? apart from your file way.

Originally Posted by waxydock

so if the number entered was 1000000.. etc there is no way to just get 1000 or even 500 digits at a time into a buffer until ive looped through them all? apart from your file way.

Never say never!

Easier, certainly. The first pass does the checking, sets everything up to be read as a string, which printf() will very nicely change into regular digits just by using %d, instead of %c.

To do it in one pass you'd need a loop (including a counter), to check each char (is it a digit or what?), then you'd need some memory to hold this (maybe), outrageously huge number.

Array's won't always be able to handle a number with a million digits (and is the million figure really the upper limit?). I wouldn't trust a linked list with a million nodes, either. Sure, each node could handle several digits, but now you're introducing another complexity to the code stew. Anything that handles the digits as something in "chunks", other than as a "stream", is going to have to handle putting the number back together again, too.

The writing and reading from the HD would be quite fast (done in large bunches naturally by the HD controller), so you wouldn't be losing much time. The HD could be working while your input of further numbers, was still going on.

Can you think of something better?

Adak

i thought my was good good.. but i think i misunderstood on how to do this. I thought that this line would keep getting 1000 digits at a time from the input. Am i wrong?

Code:

if (fgets(myArray, maxSize, stdin) == NULL)

This is the sudo code they gave in the question...

Code:

let the length of a buffer = x

read digits as many as x from standard input

while ( the buffer contains some digits ) do {

   //whatever

   read next x digits from standard input
}

The teacher makes it so simple, he said we should use fgetc or fgets .. those type of functions .. thats why i don't think i need to do that file stuff you mentioned..

anyone have any ideas on how to implement this sudo code?

Originally Posted by waxydock

This is the sudo code they gave in the question...

Code:

let the length of a buffer = x

read digits as many as x from standard input

while ( the buffer contains some digits ) do {

   //whatever

   read next x digits from standard input
}

The teacher makes it so simple, he said we should use fgetc or fgets .. those type of functions .. thats why i don't think i need to do that file stuff you mentioned..

anyone have any ideas on how to implement this sudo code?

It's elementary to do the above, but NOT (imo), for a million digits. Contrary to our politicians in Washington, a million (bucks in their case, digits in ours ), is really respected as a VERY large number.

Did your teacher mention what kind of data structure he thought would be suited to hold a million digits?

There are ways to pack bytes with digits, but it's WAY above your skill in C, and I've done it like once, years ago. Hard drive is there spinning anyway, and has plenty of storage these days.

Adak

but you never store the million digits right? you just store 1000 at a time, or am i wrong?

also can an int array hold 1000000 + digits?

It's not like the solution has already been mentioned several times in this thread. Each call to fgets(..., 1001, stdin) reads up to 1000 digits (+ 1 for the \0), only the last call will read less than 1000 digits (+ the final fgets call that reads nothing and will exit the loop)