优先级队列功能比较

在下面的代码中，当在优先级队列中使用时，比较项是被推送的项目吗？ 因此，在Mycomp函数中，pair &a要添加的对象和pair &b，是否已经在队列中并与之进行比较？

class Solution {
public:

struct Mycomp {
bool operator()(const pair<int, string> &a, const pair<int, string> &b){

if(a.first != b.first) { // comparing the frequency if it is not same then return the one with smallest frequency
return a.first > b.first;
}else{
// if frequency are same then compare the alphabetical order - should return the largest one as the idead is to pop smallest frequency with 
// largest alphabetical order
return a.second < b. second;
}
}
};
vector<string> topKFrequent(vector<string>& words, int k) {

//defining a map to keep track of the frequency of the words
std::unordered_map<string, int> hashMap;
for( auto word : words) {
hashMap[word]++;
}

// Now we use the concept of priority queue 
std::priority_queue<pair<int, string>,std::vector<pair<int,string>>, Mycomp> pq ;

for(auto ele : hashMap) {
pq.push({ele.second, ele.first});

if(pq.size() > k) {
pq.pop(); // pop the elements with least frequency
}
}

vector<string> result;
while(k--){
result.insert(result.begin(),pq.top().second); // if you use push back, then you need to reverse the vector as pq returns the highest alpabetical order when popping.
pq.pop();
}

return result;
}
};