Merge Two Sorted Lists (Easy)
Description
Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.
Analysis
两个有序链表合并。
My Solution
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* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
if(l1==NULL && l2 ==NULL)
return NULL;
if(l1==NULL)
return l2;
if(l2==NULL)
return l1;
ListNode *head = NULL,*p;
if(l1->val<=l2->val){
head = l1;
l1 = l1->next;
}
else{
head = l2;
l2 = l2->next;
}
p = head;
while(l1!=NULL && l2!=NULL){
if(l1->val<=l2->val){
p->next = l1;
l1 = l1->next;
p = p->next;
}
else{
p->next = l2;
l2 = l2->next;
p = p->next;
}
}
while(l1!=NULL){
p->next = l1;
l1 = l1->next;
p = p->next;
}
while(l2!=NULL){
p->next = l2;
l2 = l2->next;
p = p->next;
}
p->next = NULL;
return head;
}
};
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