LeetCode-链表

23. 合并K个升序链表

 [LeetCode] 23. Merge k Sorted Lists 合并k个有序链表 - Grandyang - 博客园

class Solution {
public:
    ListNode* mergeKLists(vector<ListNode*>& lists) {
        if (lists.empty())
            return nullptr;
        int n = lists.size();
        while (n > 1){
            int k = (n + 1) / 2;
            for (int i=0; i<n/2; i++){
                lists[i] = merge(lists[i], lists[i+k]);
            }
            n = k;
        }
        return lists[0];
    }

    ListNode* merge(ListNode* l1, ListNode*l2){
        ListNode* dummy = new ListNode(-1);
        ListNode* cur = dummy;
        while(l1 && l2){
            if (l1->val < l2->val){
                cur->next = l1;
                l1 = l1->next;
            } else {
                cur->next = l2;
                l2 = l2->next;
            }
            cur = cur->next;
        }
        if (l1){
            cur->next = l1;
        }
        if (l2){
            cur->next = l2;
        }
        return dummy->next;
    }
};