Thread: can you give another logic?

if the numbers are non-zero integers we can do this:

first, convert all the numbers to unsigned integers. This will get us rid of negative numbers.

then, if floor(x / y) = 0, x < y

then just do:

Code:

int max(int x, int y)
{
    unsigned signx = (unsigned)x;
    unsigned signy = (unsigned)y;

    if ( !(signx / signy) )
        return y;

    return x;
}

int main()
{
    int x, y, z;

    scanf("%d %d %d", &x, &y, &z);

    printf("%d", max(max(x, y), z));
    
    return 0;
}

If the numbers can be 0, one way would be to check the denominator. If it is 0, return the other number:

Code:

int max(int x, int y)
{
    // 1 = negative, 0 = positive
    unsigned signx = (unsigned)x;
    unsigned signy = (unsigned)y;

    if ( signy )
        if ( !(signx / signy) )
            return y;

    return x;
}

I believe that

Code:

unsigned signx = (unsigned)x;

for signx < 0 will give you a very large number. Which means that it will probably be bigger than any positive number. So you will get actually

max (abs(x), abs(y), abs(z))

which might not be the case


EDIT: I believe there should be a fix like this

Code:

int a = -1;
unsigned fix = (unsigned)a;
if (a - fix == 0) 
   positive;

EDIT2: the

Code:

 if ( signy )

will sho if it is !=0 not if it is negative

True. My method only works if all the numbers have the same sign.

However, it is easy to check the sign bit and act accordingly: if all the numbers are either positive or negative, my method does work (it's not exactly the maximum of the absolute values, because -1 interpreted as unsigned is bigger than -3 as unsigned for example). If there is a negative number, then the answer is the max of the positives. If there are two negatives, then the answer is the positive.

Edit to answer your edits:

Yes, I am checking to see if signy != 0. If it is 0, then signx / signy would crash the program. If it is 0, I just return x. I don't really understand your first edit. Could you explain why you did that please?

Here's one technique that you can use to get you there, which doesn't rely on two's complement representation:

Code:

if a mod b equals a, then a is less than b

Edit: Assuming we're talking about positive numbers here of course.

Originally Posted by crocker

Hi friends,

i tried to solve the logics for the question " write a c program to find max of 3 numbers with out using ">" and "ternary operators" "

Why do they not let you use ?: but they allow if/else? That doesn't really make sense.


Quzah.