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45 | /**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* mergeTwoLists(ListNode* list1, ListNode* list2) {
ListNode* startNode = new ListNode(5566);
ListNode* curNode = startNode;
while (list1 != nullptr && list2 != nullptr) {
if (list1->val <= list2->val) {
curNode->next = list1;
list1 = list1->next;
}
else {
curNode->next = list2;
list2 = list2->next;
}
curNode = curNode->next;
}
if (list1 != nullptr && list2 == nullptr)
curNode->next = list1;
else if (list1 == nullptr && list2 != nullptr)
curNode->next = list2;
return startNode->next;
}
ListNode* mergeKLists(vector<ListNode*>& lists) {
if (lists.size() == 0)
return nullptr;
ListNode* head = lists[0];
for (int i = 1; i < lists.size(); i++)
head = mergeTwoLists(head, lists[i]);
return head;
}
};
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