Thread: C puzzle

Sounds like a weird puzzle, but if the following is your condition, it'll print "Hello World":

Code:

(printf("Hello ") != 6)

Or if you wanted no spaces:

Code:

(printf("Hello") != 5)

I don't think that's what the writer(s) of the challenge had in mind, though.

Think I found the challenge: http://paonethestar.wordpress.com/20...ing-puzzles-2/

Perhaps they did want a solution like this.

the only thing that i can think about is that when the condition "holds". In other words, the condition is true or represent a digit that is not '0'

Originally Posted by kky2k

how about this....

Code:

if(!printf("hello"))

printf("hello");

else

printf("world);

Isn't that what MacGyver suggested :\

Originally Posted by printf return value

printf - On success, the total number of characters written is returned.

So 5 != 5 is the same as !5

Only if somehow printf() fails :|

If you want the expression to always evaluate to false you should do this:
if(printf("Hello "),false)

Originally Posted by King Mir

If you want the expression to always evaluate to false you should do this:
if(printf("Hello "),false)

You should? Really!??!

No.

Originally Posted by zacs7

Only if somehow printf() fails :|

Exactly. If printf() fails, then you probably shouldn't expect the next printf() to succeed. That means no part of the message should be printed. There is no reason to assume printf() will fail for this example since the challenge was to get "hello world" to the screen by a condition in a snippet of code that already relies upon printf() working successfully.

Therefore, I think it safe to assume for this example that printf() will not fail, for the sake of the challenge.

Originally Posted by King Mir

If you want the expression to always evaluate to false you should do this:
if(printf("Hello "),false)

Inventing additions to the C language today, are we?

Originally Posted by MacGyver

Exactly. If printf() fails, then you probably shouldn't expect the next printf() to succeed. That means no part of the message should be printed. There is no reason to assume printf() will fail for this example since the challenge was to get "hello world" to the screen by a condition in a snippet of code that already relies upon printf() working successfully.

Therefore, I think it safe to assume for this example that printf() will not fail, for the sake of the challenge.

True, it says print "Hello World" not "ello World" or something along those lines - it's Hello World or nothing.

Inventing additions to the C language today

well... this code WILL work:

Code:

#include <stdio.h>

int main()
{
	if(printf("Hello "),0)
	{
	}
	else
		printf( "World!\n");

	return 0;
}

If you want to print "Hello" and "world", an if-else construct, by definition, isn't going to achieve that.

It will print one or the other.

EDIT: sorry, reading the thread properly, I just realised the puzzle. As has been said, make the if fail by testing for an amount of chars not equal to 6.

Originally Posted by MacGyver

Inventing additions to the C language today, are we?

C99 does have the boolean type, and defines true and false in stdbool.h

If you consider a standard header to be part of the language, which you must since you're using printf(), then false is perfectly OK.