Question

Im working on a program that inputs book data in a struct, and deletes an element upon the user’s request. However, Im having difficulty figuring out the best way to do delete the requested book. Do you think Im headed in the right direction?

struct Data{                        //struct of data
    string title;
    string author;
    string publisher;
};

void remove (Data *ptr, string title, string author, string publisher, int num)
{
    string book_rem;
    cout << "What book do you want to remove?" << endl;
    getline (cin, book_rem);

    for (int i=0;i<num;i++)
    {
        if (ptr[i].title == book_rem) // check for equality
            {
               for (int j = 0; j < num; j++)  //shift over elements in new array
               ptr[j] = ptr[j+1];
               ptr[j-1] = 0;
            }   
        else 
           {
            cout << "book not found!" << endl;
           }
    }
}

I know my logic is off ?.. but my tutor said i was close..if you have any good resources or links please send them this way these pointers have me slightly confused on the best way to get it done.

Answer 1

Well in the for loop, you are marking that the book wasn’t found immediately after the first if (ptr[i].title == book_rem). What if the book is present as the 2nd element or thereafter.

You should divide your work into two parts as follows:

• Search for the book.
• Delete it if found, otherwise print “Not Found”.

He is what it may look like inside the loop:

for (int i = 0 ; i < num ; i++) {
    if (ptr[i].title == book_rem) // check for equality
    {
        break;
    }  
}

And then outside the loop, check if the book was found, and do the required stuff:

if ( i < num ) {// Book was found as i is less than size.
    /*
        You don't have to shift over elements in the array.
        I'm assuming your list isn't sorted, so you can just transfer 
        the last element in the array to the position pointed by i, and 
        then decrement the size by 1. 
    */
    // Copy all the elements from ptr[num-1] to ptr[1].
    num = num - 1;
}
else {
    cout << "book not found!" << endl;
}