Validating input to an array

Question

I am trying to validate the input of the array to only allow an input of only one single digit integer (either 2 or 3) at each index of the array. For example a = [2,3,2,3,2,2,2,2,2,3]. My attempt is below.

int main()
{
        int a[10];
        int b;
        bool c= false;
        printf( "Please the 10 values: \n");
        while(c)
        {
            for(b=0;b<10;b++)
            {

                scanf("%d", &a[b]);//enter each value individually
                if(&a[b]==2 || &a[b]==3)
                {
                    c= true;
                }
                else
                {
                    printf("please the value");
                    scanf("%d", &a[b]);
                    c= false;
                }
            }

        }
}

Sourav Ghosh · Accepted Answer · 2015-04-21 21:22:42Z

2

If you want to check the value, you have to change your code

if(&a[b]==2 || &a[b]==3)

to

if((a[b]==2) || (a[b]==3))   //no need for address of (&) operator

However, for an array like int a[10];, using

 for(b=0;b<32;b++)

will overrun the allocated memory and you'll run into undefined behavior.

That said, the else part is not checking the validity of the repeated input. You need to take care of that, too.

Also, the recommended signature of main() is int main(void).

edited Apr 21, 2015 at 21:22

answered Apr 21, 2015 at 20:57

Sourav Ghosh

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2 Comments

user2359244 Over a year ago

Ahh it was supposed to be 32 at first but I changed it to 10 I'll edit the code now. My mistake sorry

C0deH4cker Over a year ago

You are using unnecessary parentheses. Just do if(a[b] == 2 || a[b] == 3)

user3121023 · Accepted Answer · 2015-04-21 21:40:31Z

0

Increment the counter b when there is a correct value.
scanf will return the number of items successfully scanned. In this case one.
If scanf does not return one, the else will read a character and then scanf can try again.

int main()
{
    int a[10];
    int b = 0;
    printf( "Please the 10 values: \n");
    while(b < 10)
    {
        printf( "enter value for a[%d]\n", b);
        if ( ( scanf("%d", &a[b])) == 1) {//enter each value individually
            if(a[b]==2 || a[b]==3)
            {
                b++;//correct value increment b
            }
        }
        else //scanf failed to read an int
        {
            getchar ( );//read a character and try again
        } 
    }
}

edited Apr 21, 2015 at 21:40

answered Apr 21, 2015 at 21:08

user3121023

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2 Comments

user2359244 Over a year ago

When I enter a letter I still get an error. Is there anyway to avoid that?

user2359244 Over a year ago

I'm also trying to solve the problem using for validating for loops.

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