C ++类型为char的输入，类型为int的输出

Question

I am taking my very first C++ class and I am stuck. I would really appreciate some help from you experienced programmers.

The assignment is creating a blackjack-scoring program. Not a very realistic one, but hey. The user inputs how many cards he wants and then the values of each of those cards. The assignment specifies that the inputs should be in type char . So if the user has a 2 card they enter 2, but that 2 is actually char and must be converted to int . Or they would enter "Q" if they have a queen and my program is supposed to convert that Q to ten points for scoring. I cannot figure out what is the right way to do this. The assignment suggests I will use either a switch statement or nested if-else statement, but I am afraid I don't understand switch very well from the book examples.

So here's a tiny bit of my attempts at switch. *points_for_card* is of type char and *number_value* is int.

switch (points_for_card)
{    
case '2':
   number_value = 2  ;
   break;
case '3':
   number_value = 3  ;
   break;

// ETC
}

So what I am going for here is: if the user enters '3' as a char, it becomes int 3. But maybe this is not how switch works at all.

The thing is, my program compiles and works, but returns weird crazy huge numbers. If I move points_for_card to int instead of char , then the arithmetic works perfectly for whatever numbers I enter, because at that point it's just adding them together.

I hope I explained this ok, will clarify as much as possible if necessary.

Answer 1

it can be something like this code:

if (points_for_card >= '1' && points_for_card <= '9'){
    number_value = points_for_card - '0'; // convert to number
}else if (points_for_card == 'Q'){
    ...
}

Answer 2

A map comes to mind. You can store the scores directly, or you can make one map to look up the card type and other maps to associate other information (like score) to each card. Here's the baby example:

std::map<char, int> scores;

scores['Q'] = 10; scores['A'] = 13; scores['2'] = 2; // etc.

char c;

std::cout << "Please enter a card: ";
std::cin >> c;

std::cout << "Your card has score " << scores[c] << std::endl;

Oftentimes when your heart says "switch", your brain should say "map" :-)

Personnally I'd define an enum ECardType { Card_2, ..., Card_10, Card_Jack, ... }; and have one map be std::map<char, ECardType> , and then other maps from card type to secondary information like scores.

Answer 3

How are you taking inputs into points_for_card ?

Your input should be cin >> points_for_card ;

Instead of comparing a character to a character, you can also compare it to the ASCII value of a character. For example,

char letter = 'A'
if(letter == 65){
cout << "Match";
}

The above code will output "Match!".

Also, your switch statements are perfectly worded. The problem lies elsewhere in your program, so please provide the relevant source. Another point related to your program but not your problem: How are you dealing with Aces ? You know that they can be counted as either 1 or 11, depending on the player's hand value, right ?