Thread: line transit in array

Hi,
I need to take an array & an integer from stdin. the integer will set how much will a lines in array move towards upwards.
example:

input:

line 0 1 12 5
line 1 7 5 3
line 2 9 7 2

integer=1

line 0 7 5 3
line 1 9 7 2
line 2 1 12 5

this is what i wrote. it doesnt work very well...

Code:

#include<stdio.h>
#define M 20

int A[M][M]={0},i,j,m,x;
void main()
{
puts ("enter the dimension of array A");
scanf ("%d", &x);
printf ("\nenter %d positive integers for array A\n", x*x);
for (i=0;i<x;i++)
        {
        for (j=0;j<x;j++)

        scanf ("%d", &A[i][j]);
        }
printf ("how much lines you want to move in the array? no. should be smaller then %d\n",x);
scanf ("%d", &m);
if (m>x||m<0)
	puts ("no. to big");

else
	{
	for (j=1;j<=x;j=j-m)
		for (i=0;i<x;i++)

			printf ("%d", A[i][j]);
        printf ("\n");
	}
  }

what do you think?

Ronen

What about constrcting an array with undefined size??
For each line do a gets(), and read all numbers in it. End a line with enter.
If the user writes an empty string the cicle ends, then do the shift stuff.

Code:

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

int main(){
	int shift;
	int array[100][100], bckp[100];
	int xlen=100, ylen=0, xline=0, yline=0, i, j, k;
	char line[500];
	
//the newline is also read, therefore buffer flushing isn't necessary	
	scanf("%d\n", &shift);

	if(shift<1) return 0;
	
	while(1){
		fgets(line, sizeof(line), stdin);
		if(!line[0] || line[0]=='\n') break;
		n=strchr(line, '\n');
		if(n) *n=0;

		for(i=0;line[i];){
			while(line[i]==' ') i++;//skip spaces
			if(line[i]=='\n')//end of line				
				break;
			array[ylen][xline++]=atoi(line+i);
			while(isdigit(line[i])) i++;
		}
		if(xline<xlen) xlen=xline;
		xline=0;
		ylen++;
	}
	shift%=ylen;//prevent excess of cicles

//------- shifting the numbers
	while(shift-->0){
		for(i=0;i<xlen;i++) bckp[i]=array[0][i];

		for(j=0;j<ylen-1;j++){
			for(i=0;i<xlen;i++)
				array[j][i]=array[j+1][i];
		}
		for(i=0;i<xlen;i++)
			array[ylen-1][i]=bckp[i];
	}
//--------- presenting the result

	for(j=0;j<ylen;j++){
		for(i=0;i<xlen;i++)
			printf("%d\t", array[j][i]);
		puts("");
	}
	getch();
	return 0;
}

I hope if you don't mind that I post the already solved solution here... with the input stuff I sugested.

Originally Posted by xErath

What about constrcting an array with undefined size??
For each line do a gets(), and read all numbers in it.
...

Code:

...
	fflush(stdin);//clear the buffer
...
		gets(line);

I hope if you don't mind that I post the already solved solution here... with the input stuff I sugested.

You're just full of horrible ideas today, aren't you? Read the FAQs on both.

Quzah.

Hum, i knew that stuff with the buffer overflow with gets... In fact that happens to evry function that receives pointers wihout enough memory allocated. Plus VC++ libraries, which is what I use, don't have the strtok() function.
About fflush(stdin) I wasn't aware of it, although I've always doubted of it, like, sending data back to the keyboard isn't a very good thing...

So fflush(stdin) becomes
while(kbhit()) getch();

//EDIT
while(kbhit()) getch(); isn't working...
Bah.

Look in the faq for how to flush input buffer:
http://faq.cprogramming.com/cgi-bin/...&id=1043284392

>In fact that happens to evry function that receives pointers wihout enough memory allocated.
No, it happens with every function that doesn't know when to stop.

>Plus VC++ libraries, which is what I use, don't have the strtok() function.
VC++ supports the C standard library for as far back as I can remember. strtok is in <string.h>, and is a standard function so you can be guaranteed that it's there or you're free to lawsuit. Actually, I'm just kidding about the lawsuit.

>sending data back to the keyboard isn't a very good thing...
Well, the definition of a flush is writing unwritten data. That's fundamentally different from what people expect from fflush(stdin). They expect to read from the input buffer and discard. Both concepts empty the buffer, but because the two operations are totally different, one can't expect fflush(stdin) to do both. That's the logical explanation. The practical explanation is that the standard requires an output stream, so calling fflush on an input stream is undefined.

>So fflush(stdin) becomes
>while(kbhit()) getch();
From undefined to nonportable and broken. Better, but not much. The first thing you should realize is that if you need to flush the input stream, your design is already flawed. But if you really need to you can do it portably. Because everyone basically wants to terminate the line, we usually suggest testing for EOF and '\n':

Code:

int ch;
while ((ch = getchar()) != EOF && ch != '\n') {
  /* Do nothing */
}

Depending on your idea of flushing the buffer, you can modify that. However, keep in mind that flushing stdin alone may not be enough if other buffers outside of the program's control have unread data. Also keep in mind that flushing stdin is grossly antisocial.

>but vc++ says strtok undifined...
The problem is probably with how you use it then.

All buffered input will contain a newline. Unless you're using non-buffered IO, they have to press enter for the information to be read from the buffer at all. Otherwise it will just sit there. Don't believe me? Run this, but don't hit enter. Post back when it reaches the end with you not hitting enter or inputting EOF.

Code:

#include <stdio.h>
int main( void )
{
    getchar( );
    printf("If you're here, you've hit enter, no two ways about it.\n");
    return 0;
}

So in short, you have to hit enter, and as such, it will be in the input stream. Additionally, anything you input before the newline will be buffered also. Thus, the standard example, as per the FAQ, is what you want to clear your input buffer.

Code:

while( (c=getchar())!='\n' && c != EOF );

And yes, getchar can return EOF, as can be clearly demonstrated.

Quzah.

stdin->_cnt = 0;
}
And it worked fine, though I don't know if this is safe to do.

No it isn't safe, nor is it portable.