返回值时布尔检查表现异常

Question

#include <iostream> 
#include <string>

bool is_favorite(std::string word) 
{
    int isTrueCounter = 0;

    std::cout << "\nisTrueCounter: " << isTrueCounter;

    if (isTrueCounter == word.length())
    {
        return true;
    }
    else {
        for (int i = 0; i < word.length(); i++)
        {
            if (word[i] == 'a' || word[i] == 'A')
            {
                isTrueCounter++;
                std::cout << "\nisTrue +1 ";
            }
            else
            {
                if (word[i] == 'b' || word[i] == 'B')
                {
                    isTrueCounter++;
                    std::cout << "\nisTrue +1 ";
                }
                else
                {
                    if (word[i] == 'c' || word[i] == 'C')
                    {
                        isTrueCounter++;
                        std::cout << "\nisTrue +1 ";
                    }
                    else {
                        if (word[i] == 'd' || word[i] == 'D')
                        {
                            isTrueCounter++;
                            std::cout << "\nisTrue +1 ";
                        }
                        else
                        {
                            if (word[i] == 'e' || word[i] == 'E')
                            {
                                isTrueCounter++;
                                std::cout << "\nisTrue +1 ";
                            }
                            else
                            {
                                if (word[i] == 'f' || word[i] == 'F')
                                {
                                    isTrueCounter++;
                                    std::cout << "\nisTrue +1 ";
                                }
                            }
                        }
                    }
                }
            }

        } //for
    }

    std::cout << "\nisTrueCounter: " << isTrueCounter;

}

int main()
{
    std::string favWord;
    std::cout << "Please input your word: ";
    std::cin >> favWord;
    std::cout << "\nFavWord Length: " << favWord.length();
    
    if (is_favorite(favWord) == true)
    {
        std::cout << "\nThis is a favorite word!";
    }
    else
    {
        std::cout << "\nThis is NOT a favorite word!";
    }
}

这是我的代码，我试图将一个字符串传递到一个布尔函数中，如果传递的字符串满足所有条件，该函数将返回 true。 “通过”单词的资格是它只包含字母 af （无论哪种情况），因此像 AaAa 或 Cafe 或 Bad 这样的单词应该通过，但经过反复试验，即使是我知道应该通过的单词也失败了，我觉得就像我通过递增变量 (isTrueCounter) 来正确跟踪字母的限定条件一样，以计算字符串中的所有字符是否都是限定字符，但即使函数应该返回 true，也会显示 false 情况。我做错了什么？我没看到什么？当我运行此代码时，它将显示变量以帮助跟踪何时将内容添加到持有者变量中，但即使所有数字都正确，也会显示错误的情况。

Answer 1

您没有返回任何东西，您可以通过多种方式做到这一点。例如，在您的代码中，在条件不成立后立即返回 false（不在 af 中）。

bool is_favorite(std::string word) 
{
    int isTrueCounter = 0;
    std::cout << "\nisTrueCounter: " << isTrueCounter;
    if (isTrueCounter == word.length())
    {
        return true;
    }
    else {
        for (int i = 0; i < word.length(); i++)
        {
            if (word[i] == 'a' || word[i] == 'A')
            {
                isTrueCounter++;
                std::cout << "\nisTrue +1 ";
            }
            else
            {
                if (word[i] == 'b' || word[i] == 'B')
                {
                    isTrueCounter++;
                    std::cout << "\nisTrue +1 ";
                }
                else
                {
                    if (word[i] == 'c' || word[i] == 'C')
                    {
                        isTrueCounter++;
                        std::cout << "\nisTrue +1 ";
                    }
                    else {
                        if (word[i] == 'd' || word[i] == 'D')
                        {
                            isTrueCounter++;
                            std::cout << "\nisTrue +1 ";
                        }
                        else
                        {
                            if (word[i] == 'e' || word[i] == 'E')
                            {
                                isTrueCounter++;
                                std::cout << "\nisTrue +1 ";
                            }
                            else
                            {
                                if (word[i] == 'f' || word[i] == 'F')
                                {
                                    isTrueCounter++;
                                    std::cout << "\nisTrue +1 ";
                                } else {         //add this else clause
                                    return false;
                                }
                            }
                        }
                    }
                }
            }
        } //for
    }
    std::cout << "\nisTrueCounter: " << isTrueCounter;
}

但您的某些代码可以改进。

1.我不知道你为什么要添加这些行。除非 word.length() 为 0，否则这永远不会成立。

if (isTrueCounter == word.length())
{
    return true;
} 

2.不要将可以在一个 if 中写入的条件拆分为多个 if ，这是一种不好的行为。

if (word[i] == 'a' || word[i] == 'A')
{
    isTrueCounter++;
    std::cout << "\nisTrue +1 ";
}
else
{
    if (word[i] == 'b' || word[i] == 'B')
    {
        isTrueCounter++;
        std::cout << "\nisTrue +1 ";
    }

这更好。

if (word[i] == 'a' || word[i] == 'A' || word[i] == 'b' || word[i] == 'B')
{
    isTrueCounter++;
    std::cout << "\nisTrue +1 ";
}

3.您可以比较 char，而不是检查 word[i] == 'a'... 使用 >; < >= <=。

if (word[i] >= 'a' && word[i] <= 'f' || word[i] >= 'A' && word[i] <= 'F')
{
    isTrueCounter++;
    std::cout << "\nisTrue +1 ";
}

4.string 已经在 iostream 中，您不必再次导入它。

总之你的代码可以变成这样

bool is_favorite(std::string word) 
{
    int isTrueCounter = 0;
    for (int i = 0; i < word.length(); i++)
    {
        if (word[i] >= 'a' && word[i] <= 'f' || word[i] >= 'A' && word[i] <= 'F') {
            isTrueCounter++;
            std::cout << "\nisTrue +1 ";
        } else {
            return false;
        }
    }
    std::cout << "\nisTrueCounter: " << isTrueCounter;
    return true;
}