如何避免一遍又一遍地打印相同的东西？

Question

case 4:
        {
            string bookTitleDel;
            int bookPageNDel;
            int bookReviewDel;
            float bookPriceDel;

            cout << "\nPlease Enter the Title to be Deleted: ";
            cin >> bookTitleDel;
            cout << "\nTotal Number of Pages of the Book to be Deleted: ";
            cin >> bookPageNDel;
            cout << "\nPlease Enter Rating (stars): ";
            cin >> bookReviewDel;
            cout << "\nPlease Enter Price: ";
            cin >> bookPriceDel;

            for(int i=0;i<MAX_BOOKS;i++)
            {
                if((books[i].bookTitle!=bookTitleDel) && (books[i].bookPageN!=bookPageNDel) && (books[i].bookReview!=bookReviewDel) && (books[i].bookPrice!=bookPriceDel))
                {

                    cout<<"\n\nBook Doesnt Exist\n";
                    continue;

                }

            }

            for(int i=0; i<MAX_BOOKS; i++)
            {
                if((books[i].bookTitle==bookTitleDel) && (books[i].bookPageN==bookPageNDel) && (books[i].bookReview==bookReviewDel) && (books[i].bookPrice==bookPriceDel))
                {
                    a=i;
                    books[i]= {};
                    cout << "\nBook Deleted\n";
                    for(int k=a; k<MAX_BOOKS-1; k++)
                    {
                        books[k]=books[k+1];
                    }
                    break;
                }

            }

            break; //break to exit switch case #4.

如果不存在，此代码将打印“ book不存在”十次。 如何避免呢？ 我正在将输入的值与已经通过此处未显示的“添加书”选项添加的值进行比较。

Answer 1

仅当没有匹配项时才要打印“书籍不存在”，而不是在没有匹配项时才打印。

因此，如果存在匹配项，则将布尔变量设置为true（并中断），如果循环结束后没有匹配项，则打印。

编辑：伪代码

        boolean foundMatch = false;
        for(int i=0;i<MAX_BOOKS;i++)
        {
            if((books[i].bookTitle==bookTitleDel) && (books[i].bookPageN==bookPageNDel) && (books[i].bookReview!=bookReviewDel) && (books[i].bookPrice==bookPriceDel))
            {
                foundMatch = true;
                break;
            }
        }
        if (!foundMatch)
        {
            cout<<"\n\nBook Doesnt Exist\n";
        }

顺便说一句，您的代码中有一个错误。 如果相等的条件是a1 == a2 && b1 == b2 && c1 == c2 ，则该否定（如果为真，则为false）为!(a1 == a2 && b1 == b2 && c1 == c2)不是a1 != a2 && b1 != b2 && c1 != c2 。

Answer 2

代替2个for循环，使用1个for循环，并使用Patashu所说的布尔变量。

    switch = false

    for(int i=0; i<MAX_BOOKS; i++)
    {
        if((books[i].bookTitle==bookTitleDel) && (books[i].bookPageN==bookPageNDel) && (books[i].bookReview==bookReviewDel) && (books[i].bookPrice==bookPriceDel))
        {   
            switch = True
            a=i;
            books[i]= {};
            cout << "\nBook Deleted\n";
            for(int k=a; k<MAX_BOOKS-1; k++)
            {
                books[k]=books[k+1];
            }
            break;
        }

    }
    if (switch == False)
     cout<<"\n\nBook Doesnt Exist\n";