leetode23-合并k个排序链表
题目描述
合并 k 个排序链表，返回合并后的排序链表。请分析和描述算法的复杂度。
输入:
[1->4->5,
1->3->4,
2->6]
输出: 1->1->2->3->4->4->5->6
代码
class Solution {
public:
ListNode* mergeKLists(vector<ListNode*>& lists, int left, int right) {
if (right < left) return NULL;
if (right == left) return lists[left];
int mid = (left + right) / 2;
auto p1 = mergeKLists(lists, left, mid);
auto p2 = mergeKLists(lists, mid + 1, right);
ListNode head(0);
ListNode* cur = &head;
while (p1 && p2) {
if (p1->val < p2->val) {
cur->next = p1;
p1 = p1->next;
} else {
cur->next = p2;
p2 = p2->next;
}
cur = cur->next;
}
if (p1) cur->next = p1;
else if (p2) cur->next = p2;
return head.next;
}
ListNode* mergeKLists(vector<ListNode*>& lists) {
return mergeKLists(lists, 0, lists.size() - 1);
}
};
