Short programming: need help with pointers

Question

#include<stdio.h>    
int main()
{
    int i=10,a;
    while(i>0)
    {
        scanf("%d",&a);
        printf("%d\n",(a+a*a)/2);
        i--;
    }
}

Now what i want to ask is how to make it shorter? Maybe some way using pointers instead of variables? Maybe this: (a+a*a)/2 can be done better?

Answer 1

Beware what you ask for...

#include <iostream>

int main() 
{
    int a; 
    for (int i = 10;
         i-- && (std::cin >> a) && (std::cout << (a + a * a) / 2); )
        ;
} 

(this also includes error checking, which you didn't bother with)

EDIT: Chris's comments below reveal this to be a terse-programming challenge (and not about legibility, robustness etc.). His teacher claims a 54 character implementation.
Have to wonder whether that include spaces and newlines?

The tightest implementation I've got so far is:

#include<iostream.h>
int main(){for(int i=10,a;i--;)cin>>a,cout<<(a+a*a)/2;}

This uses the deprecated header iostream.h to remove the need to explicitly find cin and cout in std:: . It's still 74 characters (LF newlines on both lines).

As a thought experiment, let's assume we had a header "x" that declared functions int g() (get an int from stdin) and void p(int) (write an int to stdin). The implementation would then be...

#include<x>
int main(){for(int i=10,a;i--;)a=g(),p((a+a*a)/2);}

...which is still 64 characters.

Another technique commonly used to shorten code is preprocessor tricks, but the obvious one here - loop unrolling - doesn't look promising. It could look like...

#define X ...
int main(){X X X X X X X X X X}

...but if you compare for loop code to the #define -necessitated code...

for(int i=10,a;i--;)
#define X X X X X X X X X X X

...we're clearly going backwards.

Summarily, I simply can not imagine any approach shaving 10 characters off the <iostream.h> version above. If he has a 54-character implementation, I think the requirements must have been miscommunicated in the question. If not, I do hope Chris will post it later :-).

Answer 2

One way you can shorten this is to use a for loop instead of a while loop. Try using

for (i = 10; i > 0; --i) {

Rather than your current while statement. This eliminates the need for the i--; line.

I'm not sure what you mean by making this code shorter "using pointers" though. Adding pointers won't help here.

Using this for loop, your code would look like:

#include<stdio.h>    
int main()
{
    int i, a;
    for (i = 10; i > 0; --i)
    {
        scanf("%d",&a);
        printf("%d\n",(a+a*a)/2);
    }
}

This removes one line. The only way of removing more lines would be to make this code less readable, or by changing your code style (which is completely unnecessary).