c++ - 优先级队列 C++ 中的 "No matching member function for call to push"

Question

我现在正在尝试实现优先级队列，但我不断收到错误消息，提示 push 不是成员函数。我以前从未使用过优先级队列，所以我很确定我在某个地方搞砸了......

struct X
{
    unordered_map<string, double> distance;
    unordered_map<string, string> vertices;
};

void make(std::string source)
{
    X distance;
    X parent;
    priority_queue<X, std::vector<X>, greater<void>> pq; //i'm pretty sure there's something wrong with the templates?
    distance.distance[source] = 0;
    pq.push(std::make_pair(start, 0));

Answer 1

该类必须具有可比性，并且必须响应 < 和 > 等运算符，以便队列可以对它们进行排序:

class X {
    public:
    unordered_map<string, double> distance;
    unordered_map<string, string> vertices;
    int priority;
    bool operator< (const X& b) {
        return priority < b.priority;
    }
    bool operator> (const X& b) {
        return priority > b.priority;
    }
};

void make(std::string source) {
    priority_queue<X, vector<X>, greater<void>> pq;

    X element;
    element.distance[source] = 0;
    element.priority = 100;
    pq.push(element);
}