Thread: Logical operators help with formula

Hi guys, I have problem with this: I need program A,B,C,D:
that when I write 4 numbers program solve
truth (1)/false (0) I have "formula" ¬(A ∨ B) ∧ ¬C ∧ (C ∨ D)

I have program, but i can write whatever and everytime program write 0 (False). I am beginner in programming. Can you help me?

I have two version:

Code:

int main()
{
    printf("A,B,C,D:\n");
    int a,b,c,d;
    int first = (!(a||b));
    int second = (!(c));
    int third = (c||d);
    scanf("%d,%d,%d,%d",&a,&b,&c,&d);
    printf("%d",(!(a||b))&&(!(c))&&(c||d));
    return 0;
}

OR

Code:

int main()
{
    printf("A,B,C,D:\n");
    int a,b,c,d;
    scanf("%d,%d,%d,%d",&a,&b,&c,&d);
    result =((((!(a||b))&&(!(c))&&(c||d));
    printf("%d",result);
    return 0;
}

Originally Posted by Salem

> scanf("%d,%d,%d,%d",&a,&b,&c,&d);
Did you really type in the commas when you gave your input to the program?

If you didn't, then scanf would end early, and you would be left with garbage in your variables.

Consider

Code:

if ( scanf("%d,%d,%d,%d",&a,&b,&c,&d) == 4 ) {
  // do work
} else {
  // print error message
}

Yes I have commas in scanf.

Originally Posted by megafiddle

Your first version appears to work, but you do have three unused variables in there: "first", "second", and "third".

Each of the three combinations must be true for the total output to be true:

!(a||b) is true only if a=0 and b=0
!(c) is true only if c=0
(c||d) is true only if d=1 (c must be 0 for the second combination to be 1)

So only one set of input values will produce an output of 1:

0, 0, 0, 1

-

So, How to define
!(a||b) is true only if a=0 and b=0
!(c) is true only if c=0
(c||d) is true only if d=1 (c must be 0 for the second combination to be 1) ?
define this in integers or some with IF ?

Originally Posted by Jamesss

Yes I have commas in scanf.

Just to be clear, you are using commas between the values when you input them:

0,0,0,1 <Enter>

This will not work:

0001 <Enter>

Originally Posted by Jamesss

So, How to define
!(a||b) is true only if a=0 and b=0
!(c) is true only if c=0
(c||d) is true only if d=1 (c must be 0 for the second combination to be 1) ?
define this in integers or some with IF ?

They are already defined by the operators in the statements.

For example, ! is the NOT operator:
If you enter a value of 0 for c, then !(c) will equal 1
If you enter a value of 1 for c, then !(c) will equal 0

-

Originally Posted by megafiddle

Just to be clear, you are using commas between the values when you input them:

0,0,0,1 <Enter>

This will not work:

0001 <Enter>



They are already defined by the operators in the statements.

For example, ! is the NOT operator:
If you enter a value of 0 for c, then !(c) will equal 1
If you enter a value of 1 for c, then !(c) will equal 0

-

Ou, now i understand. So I delete commas in scanf so now I can use values : 5 2 4 5 <enter>

But still not work.

Originally Posted by laserlight

What is your current code, the test input, expected output and actual output?

I want to scanf 4 numbers and get back 0 or 1.

Code:

int main()
{
    printf("A,B,C,D:\n");
    int a,b,c,d;
    int first = (!(a||b));
    int second = (!(c));
    int third = (c||d);
    scanf("%d %d %d %d",&a,&b,&c,&d);
    (printf("%d",(!(a||b))&&(!(c))&&(c||d))
    return 0;
}

Why did you write this part?

Code:

   int first = (!(a||b));
   int second = (!(c));
   int third = (c||d);

Are you aware that you can do first && second && third in printf, and yet still analyze the parts separately? That way you can make changes that lead to the results you want.

Originally Posted by laserlight

Stop saying this. Back in post #8, I asked "What is your current code, the test input, expected output and actual output?" That is what you should provide when you try something and it doesn't work. Just saying that you tried it is not enough. Just saying that it doesn't work is not enough. What did you try and how does it not work? Posting the code that you tried answers the "what did you try"; posting the test input, expected output and actual output answers "how does it not work".


Break the problem into smaller pieces that you can solve. For example, start by hard coding test input, i.e., do not use scanf. Just write the part that does the formula and prints the result.

EDIT:
Oh, I see that you edited your post to include code. That is good. The problem is that you are performing the operations before you have read the input. I suggest something like this:

Code:

if (scanf("%d %d %d %d", &a, &b, &c, &d) == 4)
{
    printf("%d\n", !(a || b) && !(c) && (c || d));
}

You can see that Salem already suggested something similiar earlier.

Oh my god The only problem it scanf on the end... I thought that scanf order it doesnt matter. I first write all INT and after this scanf and final OUT ....I am stupid ... but now I know it for future Thanks very much for helping and strong nerves