【力扣 012】23. 合并K个升序链表

23. 合并K个升序链表

解法1：

class Solution {
public:
    ListNode* mergeKLists(vector<ListNode*>& lists) 
    {
        auto cmp = [](ListNode*& a, ListNode*& b) 
        {
            return a->val > b->val;
        };
        priority_queue<ListNode*, vector<ListNode*>, decltype(cmp) > q(cmp);
        for (auto node : lists) 
        {
            if (node) q.push(node);
        }
        ListNode *dummy = new ListNode(-1), *cur = dummy;
        while (!q.empty()) 
        {
            auto t = q.top(); q.pop();
            cur->next = t;
            cur = cur->next;
            if (cur->next) q.push(cur->next);
        }
        return dummy->next;
    }
};