Eof

[bittusrk]

How do we chech for the end of file in C and Java when taking input from the console?

[leppyr64]

Here's a helpful hint:
lmgtfy.com/?q=c%2B%2B+eof

[njames]

_

[njames]

I'm not sure about C (though I don't see any reason it shouldn't work) if you do something like

while( scanf(...) )

Your program should run until there is no more input since scanf( ) returns the number of parameters (or characters, I can't remember) that are read.

In Java you can do

while ( input.hasNext() )

where input is a Scanner object. Though don't quote me on that one since Java isn't my language of choice, but I remember doing something like this at one point.

[TripleM_sof]

No, in C/C++ scanf returns the constant EOF when it reaches the end of the file; you should compare with that rather than assuming it will be 0.

As leppy hinted at though, this is very easy to search for.. the answer in Java depends on what you are using to read input (Scanner is too slow so I hope you're not using that); the java API very explicitly tells you what happens when you reach EOF though, so just look it up..

[njames]

No, in C/C++ scanf returns the constant EOF when it reaches the end of the file; you should compare with that rather than assuming it will be 0.

As leppy hinted at though, this is very easy to search for.. the answer in Java depends on what you are using to read input (Scanner is too slow so I hope you're not using that); the java API very explicitly tells you what happens when you reach EOF though, so just look it up..

Thanks, I didn't know that about scanf.

[amaroq]

No, in C/C++ scanf returns the constant EOF when it reaches the end of the file; you should compare with that rather than assuming it will be 0.

That's not completely true, it only returns EOF if none of the requested items can be matched due to end of file or another error. If it can match some items, but not all, before end of file is reached, it returns the number of successfully matched items, not EOF.

So scanf("%d%d%d",&a,&b,&c) will return 2, not EOF, if there are only two numbers left in the input. So if you want to process an input file, reading three numbers at a time, it is safer to use:

while(scanf("%d%d%d",&a,&b,&c)==3){
   /* ... do your stuff ... */
   }

than

while(scanf("%d%d%d",&a,&b,&c)!=EOF){
   /* ... do your stuff ... */
   }

because the second version depends on the correctness of the input.

[TripleM_sof]

Hm, good point. Luckily I've never needed to know that, since there's never wasted data like that in SPOJ problems..