比较课程

Question

我有一个类，它创建1-6之间的数字和另一个类，将它们放入一个数组。如果它们是相同的，我如何比较两个数组？ （因此注释行可以工作）

#include <iostream>
#include <ctime>
#include <cstdlib>

class dice {
private:
    unsigned int number;
public:
    dice() {
        (*this).number = (rand() % 6) + 1;
        return;
    }
};

class dicemng {
private:
    unsigned int dice_count;
    dice* arr_dice;
public:
    dicemng(unsigned int k = 0) : dice_count(k) {
        arr_dice = new dice[dice_count];
        return;
    }
};

int main() {

    srand(time(nullptr));
    dicemng w1(5), w2(5);
    //std::cout << (w1 == w2) << std::endl;

    return 0;
}

感谢您的帮助！

Answer 1

课程中你需要operator ==，如下所示：

class dicemng {
    // ...
public:
    bool operator ==(const dicemng &other) const {
        if (dice_count != other.dice_count) return false;
        for (unsigned i = 0; i < dice_count; ++i)
            if (!(arr_dice[i] == other.arr_dice[i])) return false;
        return true;
    }
};

当然，也为班级骰子提供operator ==：

class dice {
    // ...
public:
    bool operator ==(const dice &other) const {
        return number == other.number;
    }
};

建议同时为这两个类提供operator !=，以便您也可以比较不平等：

class dice {
    // ...
public:
    bool operator !=(const dice &other) const {
        return !(*this == other);
    }
};

class dicemng {
    // ...
public:
    bool operator !=(const dicemng &other) const {
        return !(*this == other);
    }
};

顺便说一下。类dicemng有一个内存泄漏（它不释放内存），所以你应该提供一个析构函数并删除在构造函数中分配的数组。要完全正确，您需要提供或禁用复制构造函数和赋值运算符。这就是为什么std::vector的使用会更好，你会省去一些头疼的事情;）

Answer 2

使用std::vector并定义dicemng::operator==以使用std::vector::operator==：

#include <vector>

class dicemng {
private:
    // `dice_count` becomes redundant since you can get it with `arr_dice.size()`
    std::vector<dice> arr_dice;
public:
    dicemng(unsigned int k = 0) : arr_dice(k) { }
    bool operator==(dicemng const& rhs) const { // `rhs` == "right hand side"
        return arr_dice == rhs.arr_dice; // Compares the contents of the vectors
    }
    // Common sense says if we define `operator==` we should also define `operator!=`:
    bool operator!=(dicemng const& rhs) const {
        return !(*this == rhs); // Implemented in terms of `operator==`
    }
};

int main() {
    srand(time(nullptr));
    dicemng w1(5), w2(5);
    std::cout << (w1 == w2) << std::endl;

    return 0;
}