c++ - 输入验证不起作用

Question

我正在尝试解析来自文件的输入以表示一副标准纸牌(即 2C 表示两张梅花)。但是，我的解决方案没有按预期工作，并声明所有输入均无效。我在我的代码中看不到任何逻辑错误，所以我想征求第二意见。代码如下:

/*
 * Determines if the input string is valid.
 * 
 * A string is considered valid if it begins with either a number (2-10) 
 * or a letter (J/j, Q/q, K/k) to deetermine rank, followed by a letter to
 * determine suit (C/c, D/d, H/h, S/s).
 */
bool inputValidator(string cardData)
{
    if (cardData.length() == 2) //Input string is two characters long
    {
        if (cardData[0] < '2' || cardData[0] > '9'
            || cardData[0] != 'J' || cardData[0] != 'j'
            || cardData[0] != 'Q' || cardData[0] != 'q'
            || cardData[0] != 'K' || cardData[0] != 'k'
            || cardData[0] != 'A' || cardData[0] != 'a')
        {
            cout << "Card with data " << cardData << " has an invalid rank." << endl;
            return false;
        }
        if (cardData[1] != 'C' || cardData[1] != 'c' //Parse suit
            || cardData[1] != 'D' || cardData[1] != 'd'
            || cardData[1] != 'H' || cardData[1] != 'h'
            || cardData[1] != 'S' || cardData[1] != 's')
        {
            cout << "Card with data " << cardData << " has an invalid suit." << endl;
            return false;
        }
        return true;
    }
    else if (cardData.length() == 3) //Input string is three characters long
        //This occurs only if the number is 10.
    {
        if (cardData[0] != '1' || cardData[1] != '0') //Parse rank
        {
            cout << "Card with data " << cardData << " has an invalid rank." << endl;
            return false;
        }
        if (cardData[2] != 'C' || cardData[2] != 'c' //Parse suit
            || cardData[2] != 'D' || cardData[2] != 'd'
            || cardData[2] != 'H' || cardData[2] != 'h'
            || cardData[2] != 'S' || cardData[2] != 's')
        {
            cout << "Card with data " << cardData << " has an invalid suit." << endl;
            return false;
        }
        return true;
    }
    return false;
}

如果有任何逻辑缺陷(或更好的方法)，我将不胜感激。谢谢。

Answer 1

你正在写这样的子句:

cardData[2] != 'D' || cardData[2] != 'd'

这将始终为真，因为被测试的变量不能同时是两个值。您可能打算使用 && 而不是 ||。

您当然可以简化逻辑，例如在比较之前将输入转换为小写或大写。