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给你一个链表数组,每个链表都已经按升序排列。
请你将所有链表合并到一个升序链表中,返回合并后的链表。
示例 1:
输入:lists = [[1,4,5],[1,3,4],[2,6]]
输出:[1,1,2,3,4,4,5,6]
解释:链表数组如下:[ 1->4->5, 1->3->4, 2->6]将它们合并到一个有序链表中得到。1->1->2->3->4->4->5->6
示例 2:
输入:lists = []
输出:[]
示例 3:
输入:lists = [[]]
输出:[]
提示:
k == lists.length
0 <= k <= 10^4
0 <= lists[i].length <= 500
-10^4 <= lists[i][j] <= 10^4
lists[i]
按 升序 排列lists[i].length
的总和不超过 10^4
以下错误的选项是?
错误答案(看不懂,不知道错在哪):
struct cmp
{
bool operator()(ListNode *a, ListNode *b)
{
return a->val > b->val;
}
};
class Solution
{
public:
ListNode *mergeKLists(vector<ListNode *> &lists)
{
priority_queue<ListNode *, vector<ListNode *>, cmp> queue;
for (int i = 0; i < lists.size(); i++)
{
if (lists[i] != NULL)
queue.push(lists[i]);
}
if (queue.empty())
return NULL;
ListNode *root = new ListNode(-1);
ListNode *node;
ListNode *lastNode = root;
while (!queue.empty())
{
node = queue.top();
queue.pop();
lastNode->next = node;
lastNode = lastNode->next;
if (node->next)
queue.push(node->next);
}
lastNode->next = NULL;
return root->next;
}
};
答案有问题
这个选项连题目的示例结果都不对。
class Solution
{
public:
struct Status
{
int val;
ListNode *ptr;
bool operator<(const Status &rhs) const
{
return val > rhs.val;
}
};
priority_queue<Status> q;
ListNode *mergeKLists(vector<ListNode *> &lists)
{
for (int i = 0; i < lists.size() - 1; i++)
{
lists[i + 1] = lists[i + 1]->next;
}
for (auto node : lists)
{
if (node)
q.push({node->val, node});
}
ListNode head, *tail = &head;
while (!q.empty())
{
auto f = q.top();
q.pop();
tail->next = f.ptr;
tail = tail->next;
if (f.ptr->next)
q.push({f.ptr->next->val, f.ptr->next});
}
return head.next;
}
};