I have a piece of code here :

     printf("Enter only parenthesis to arr or anything else to exit\n");
    
     scanf(" %c", &data);

    if (data != '(' || data != ')' || data != '[' ||
        data != ']' || data != '{' || data != '}')
    {
        printf("\nExit scanning \n");
        return;
    }

My problem that no matter what i do when I enter any parenthesis it enters the "if" condition. I also tried getchar() but nothing worked either. Can you tell what's wrong I can't understand

CodePudding user response：

The problem is resolved simply.

First of all write the condition for which the input must satisfy

if (data == '(' || data == ')' || data == '[' ||
    data == ']' || data == '{' || data == '}')

Now negate it

if ( !( data == '(' || data == ')' || data == '[' ||
        data == ']' || data == '{' || data == '}' ) )

and open the parentheses and you will get

if (data != '(' && data != ')' && data != '[' &&
    data != ']' && data != '{' && data != '}')
{
    printf("\nExit scanning \n");
    return;
}

That is all.

Another approach is to use standard string function strchr declared in header <string.h> as for example

if ( strchr( "()[]{}", data ) == NULL )
{
    printf("\nExit scanning \n");
    return;
}

Or if the user can enter the code 0 then

if ( data == '\0' || strchr( "()[]{}", data ) == NULL )
{
    printf("\nExit scanning \n");
    return;
}