C++学习笔记-三元运算符

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static int s_Level = 1;
static int s_Speed = 2;

int main()
{
    // 传统的if-else写法
    if (s_Level > 5)
        s_Speed = 10;
    else
        s_Speed = 5;
    
    // 使用三元运算符的简洁写法
    s_Speed = s_Level > 5 ? 10 : 5;
    
    std::cout << s_Speed << std::endl;
}

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int main()
{
    int score = 85;
    
    // 根据分数判断等级
    std::string grade = score >= 90 ? "A" : 
                       score >= 80 ? "B" : 
                       score >= 70 ? "C" : "D";
    
    std::cout << "Grade: " << grade << std::endl;
}

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void PrintMessage(bool isError)
{
    std::cout << (isError ? "Error: " : "Info: ") << "Operation completed" << std::endl;
}

int main()
{
    PrintMessage(true);   // 输出: Error: Operation completed
    PrintMessage(false);  // 输出: Info: Operation completed
}

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int GetMax(int a, int b)
{
    return a > b ? a : b;
}

int GetAbsolute(int value)
{
    return value < 0 ? -value : value;
}

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#include <vector>

int main()
{
    std::vector<int> numbers = {1, 2, 3, 4, 5};
    
    // 安全访问数组元素
    int index = 10;
    int value = index < numbers.size() ? numbers[index] : -1;
    
    std::cout << "Value: " << value << std::endl;  // 输出: Value: -1
}

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int main()
{
    int temperature = 25;
    
    // 嵌套三元运算符
    std::string weather = temperature > 30 ? "Hot" :
                         temperature > 20 ? "Warm" :
                         temperature > 10 ? "Cool" : "Cold";
    
    std::cout << "Weather: " << weather << std::endl;
    
    // 对于复杂逻辑，建议使用if-else
    std::string recommendation;
    if (temperature > 30) {
        recommendation = "Stay indoors with AC";
    } else if (temperature > 20) {
        recommendation = "Perfect for outdoor activities";
    } else if (temperature > 10) {
        recommendation = "Wear a light jacket";
    } else {
        recommendation = "Bundle up!";
    }
}

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int main()
{
    bool condition = true;
    
    // 正确：两个分支都是int类型
    int result1 = condition ? 10 : 20;
    
    // 正确：可以隐式转换为同一类型
    double result2 = condition ? 10 : 20.5;  // int可以转换为double
    
    // 正确：都可以转换为string
    std::string result3 = condition ? "Hello" : std::string("World");
    
    // 注意：确保类型兼容
    auto result4 = condition ? 10 : 20.5;  // result4的类型是double
}

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int Add(int a, int b) { return a + b; }
int Multiply(int a, int b) { return a * b; }

int main()
{
    bool useAdd = true;
    
    // 选择不同的函数
    auto operation = useAdd ? Add : Multiply;
    
    int result = operation(5, 3);
    std::cout << "Result: " << result << std::endl;  // 输出: Result: 8
}

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// 好的使用方式
int max = a > b ? a : b;
std::string status = isOnline ? "Online" : "Offline";

// 不推荐的使用方式（太复杂）
int result = (a > b && c < d) ? (x * y + z) : (calculateComplexValue(a, b, c));

// 应该改为if-else
int result;
if (a > b && c < d) {
    result = x * y + z;
} else {
    result = calculateComplexValue(a, b, c);
}