每天坚持写几道leetcode
今天的题目是23,24打卡链表，medium难度
最近几天有点懒散，对leetcode有些放松了，但是尝试了写几道medium题目，加油坚持住
描述：Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.
例子：
1
2
3
4
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7
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Input:
[
1->4->5,
1->3->4,
2->6
]
Output: 1->1->2->3->4->4->5->6
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代码：
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ListNode* Solution23::compare(ListNode* l1,ListNode* l2)
{
if(l1 == nullptr)return l2;
if(l2 == nullptr)return l1;
ListNode *res = new ListNode(-1);
ListNode *_res = res;
ListNode* p = l1;
ListNode* q = l2;
while(p != nullptr &&q != nullptr)
{
if(p->val < q->val)
{
res->next = p;
p = p->next;
}
else if(p->val > q->val)
{
res->next = q;
q = q->next;
}
else
{
res->next = p;
p = p->next;
res = res->next;
res->next = q;
q = q->next;
}
res = res->next;
}
if(q != nullptr)
res->next = q;
if(p != nullptr)
res->next = p;
return _res->next;
}
ListNode* Solution23::mergeKLists(vector<ListNode*>& lists)
{
if(lists.size() == 0)
return nullptr;
ListNode* res = lists[0];
int i= 1;
while(i < lists.size())
{
ListNode *temp = lists[i];
res = compare(res,temp);
++i;
}
return res;
}
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题目：24. Swap Nodes in Pairs
描述：Given a linked list, swap every two adjacent nodes and return its head.
例子：
1
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Given 1->2->3->4, you should return the list as 2->1->4->3.
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代码：
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ListNode* Solution24::swapPairs(ListNode* head)
{
ListNode *res = new ListNode(-1);
res->next = head;
ListNode *_res = res;
while(_res->next !=NULL && _res->next->next != NULL)
{
ListNode *p = _res->next;
_res->next = p->next;
p->next = _res->next->next;
_res->next->next = p;
_res = _res->next->next;
}
return res->next;
}
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