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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) {
ListNode * head;
if(l1 == NULL){
return l2;
}
if(l2 == NULL){
return l1;
}
if(l1 && l2){
if(l1->val < l2->val){
head = l1;
l1 = l1->next;
}
else{
head = l2;
l2 = l2->next;
}
}
ListNode *cur = head;
while(l1 && l2){
if(l1->val < l2->val){
cur->next = l1;
cur = cur->next;
l1 = l1->next;
}
else{
cur->next = l2;
cur = cur->next;
l2 = l2->next;
}
}
if(l1){
cur->next = l1;
}
if(l2){
cur->next = l2;
}
return head;
}
};
