增加和减少优先级队列的模板函数

Question

我想编写一个模板函数来打印递增和递减优先级队列。目前我已经将其实现为

void print_queue1(priority_queue<int> q, string s){
    cout << "Value of prior queue " << s << " is : [";

    while(!q.empty()){
        cout << " " << q.top() << ",";
        q.pop();
    }
    cout << "]" << endl;
}


// min-heap
void print_queue2(priority_queue<int, vector<int>, greater<int>> q, string s){
    cout << "Value of prior queue " << s << " is : [";

    while(!q.empty()){
        cout << " " << q.top() << ",";
        q.pop();
    }
    cout << "]" << endl;
}

有什么方法可以编写一个可以做到这一点的模板函数吗？

Answer 1

您可以为此使用 variadic function template。由于无论队列类型如何，逻辑都是相同的，我们可以接受任何类型的队列，例如

template <typename... Params>
void print_queue(priority_queue<Params...> q, string s){
    cout << "Value of prior queue " << s << " is : [";

    while(!q.empty()){
        cout << " " << q.top() << ",";
        q.pop();
    }
    cout << "]" << endl;
}

这里，Params会由编译器从提供给你的priority_queue的模板参数中推导出来，并为每个不同的参数集戳出一个具体的函数。

Answer 2

模板 class std::priority_queue 使用 three template type parameters.

template<
    class T,
    class Container = std::vector<T>,
    class Compare = std::less<typename Container::value_type>
> class priority_queue;

您可以在函数中使用相同的三个参数来接受 std::priority_queue 的任何实例化。

template<class T, class Container, class Compare>
void print_queue(priority_queue<T,Container,Compare> q, string s){
    cout << "Value of prior queue " << s << " is : [";

    while(!q.empty()){
        cout << " " << q.top() << ",";
        q.pop();
    }
    cout << "]" << endl;
}

或者，您可以remove/restrict其中任何一个来强制执行优先级队列的子集..

template<class Container, class Compare>
void print_queue(priority_queue<int,Container,Compare> q, string s){
    // This function is really only designed for priority queues of int!
    cout << "Value of prior queue " << s << " is : [";

    while(!q.empty()){
        cout << " " << q.top() << ",";
        q.pop();
    }
    cout << "]" << endl;
}

增加和减少优先级队列的模板函数

Template function for increasing and decreasing priority queue

c++

templates

priority-queue