leetcode 23. Merge k Sorted Lists

递归地调用21题两个链表归并排序来实现多个链表的归并排序。

struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2) {
struct ListNode* pointer1=l1;
struct ListNode* pointer2=l2;
struct ListNode* merged=NULL;
struct ListNode* temp=NULL;
struct ListNode* mergedPointer=NULL;
while(pointer1!=NULL||pointer2!=NULL)
{
if(pointer1!=NULL&&pointer2!=NULL)
{
if(pointer1->val<=pointer2->val)
{
temp=(struct ListNode*)malloc(sizeof(struct ListNode));
temp->next=NULL;
temp->val=pointer1->val;
pointer1=pointer1->next;

}
else
{
temp=(struct ListNode*)malloc(sizeof(struct ListNode));
temp->next=NULL;
temp->val=pointer2->val;
pointer2=pointer2->next;
}
}
else if(pointer1!=NULL)
{
temp=(struct ListNode*)malloc(sizeof(struct ListNode));
temp->next=NULL;
temp->val=pointer1->val;
pointer1=pointer1->next;
}
else
{
temp=(struct ListNode*)malloc(sizeof(struct ListNode));
temp->next=NULL;
temp->val=pointer2->val;
pointer2=pointer2->next;
}
if(merged==NULL)
{
merged=temp;
mergedPointer=temp;
}
else
{
mergedPointer->next=temp;
mergedPointer=temp;
}
}
return merged;
}
struct ListNode* mergeKLists(struct ListNode** lists, int listsSize)
{
struct ListNode **l1,**l2;
struct ListNode *pointer,*left,*right;
int mid,i;
mid=listsSize/2;
if(lists==NULL||listsSize==0)
return NULL;
else if(listsSize==1)
return lists[0];
else
{
l1=lists;

l2=&lists[mid];
left=mergeKLists(l1,mid);
right=mergeKLists(l2,listsSize-mid);
return mergeTwoLists(left,right);
}
}