模板

#include<stdio.h>

#include<algorithm>

#include<queue>

 

using namespace std;

 

struct node{

    int num;

    node(int i){

        num = i;

    }

};

 

priority_queue<node>key;

 

bool operator <(node a ,node b){

    return a.num<b.num;

}

 

 

int main(){

    key.push(node(1));

    key.push(node(4));

    printf("%d ",key.top().num);

    key.pop();

    key.push(node(2));

    key.push(node(3));

    printf("%d ",key.top().num);

}

 

 

 

=============================================================================

struct compare {
    bool operator()(const ListNode* l, const ListNode* r) {
        return l->val > r->val;
    }
};
ListNode *mergeKLists(vector<ListNode *> &lists) { //priority_queue
    priority_queue<ListNode *, vector<ListNode *>, compare> q;
    for(auto l : lists) {
        if(l)  q.push(l);
    }
    if(q.empty())  return NULL;

    ListNode* result = q.top();
    q.pop();
    if(result->next) q.push(result->next);
    ListNode* tail = result;           
    while(!q.empty()) {
        tail->next = q.top();
        q.pop();
        tail = tail->next;
        if(tail->next) q.push(tail->next);
    }
    return result;
}