1、C
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* struct ListNode *next;
* };
*/
struct ListNode* mergeTwoLists(struct ListNode* list1, struct ListNode* list2){
if(list1==NULL)return list2;
if(list2==NULL)return list1;
struct ListNode* head = (struct ListNode*)malloc(sizeof(struct ListNode));
head->next = NULL;
head->val = -1;
struct ListNode*p = head;
while(list1!=NULL&&list2!=NULL){
if(list1->val<=list2->val){
p->next = list1;
list1 = list1->next;
}
else{
p->next = list2;
list2 = list2->next;
}
p = p->next;
p->next = NULL;
}
if(list1!=NULL){
p->next = list1;
}
else{
p->next = list2;
}
return head->next;
}
2、C++
/**
* 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) {
if(list1==nullptr)return list2;
if(list2==nullptr)return list1;
ListNode *head = new ListNode(-1);
ListNode* p = head;
while(list1!=nullptr&&list2!=nullptr){
if(list1->val<=list2->val){
p->next = list1;
list1 = list1->next;
}
else{
p->next = list2;
list2 = list2->next;
}
p = p->next;
p->next = nullptr;
}
if(list1!=nullptr){
p->next = list1;
}
if(list2!=nullptr){
p->next = list2;
}
return head->next;
}
};
3、JAVA
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode() {}
* ListNode(int val) { this.val = val; }
* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
if(list1==null)return list2;
if(list2==null)return list1;
ListNode head = new ListNode(-1);
ListNode p = head;
while(list1!=null&&list2!=null){
if(list1.val<=list2.val){
p.next = list1;
list1 = list1.next;
}
else{
p.next = list2;
list2 = list2.next;
}
p = p.next;
p.next = null;
}
if(list1!=null){
p.next = list1;
}
if(list2!=null){
p.next = list2;
}
return head.next;
}
}
4、Python
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class Solution(object):
def mergeTwoLists(self, list1, list2):
"""
:type list1: Optional[ListNode]
:type list2: Optional[ListNode]
:rtype: Optional[ListNode]
"""
if list1 is None:return list2
if list2 is None:return list1
head = ListNode()
p = head
while list1 is not None and list2 is not None:
if list1.val<=list2.val:
p.next = list1
list1 = list1.next
else:
p.next = list2
list2 = list2.next
p = p.next
p.next = None
if list1 is not None:
p.next = list1
if list2 is not None:
p.next = list2
return head.next