leetcode-----23. 合并K个排序链表

• 链接：https://leetcode-cn.com/problems/merge-k-sorted-lists/

代码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    struct Cmp {
        bool operator() (ListNode*a, ListNode* b) {
            return a->val > b->val;
        }
    };
    ListNode* mergeKLists(vector<ListNode*>& lists) {
        priority_queue<ListNode*, vector<ListNode*>, Cmp> heap;
        auto dummy = new ListNode(-1), tail = dummy;
        for (auto l: lists) if (l) heap.push(l);

        while (heap.size()) {
            auto t = heap.top();
            heap.pop();
            tail = tail->next = t;
            if (t->next) heap.push(t->next);
        }
        return dummy->next;
    }
};