[leetcode刷题系列]Merge Two Sorted Lists

/**
* 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) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if(l1 == 0)
return l2;
if(l2 == 0)
return l1;
ListNode * ret, *cur;
if(l1->val < l2->val){
ret = l1;
cur = l1;
l1 = l1->next;
}else{
ret = l2;
cur = l2;
l2 = l2->next;
}
while(l1 != 0 || l2 != 0){
if(l1 == 0){
cur->next = l2;
return ret;
}
if(l2 == 0){
cur->next = l1;
return ret;
}
if(l1->val < l2->val){
cur->next = l1;
cur = l1;
l1 = l1->next;
}else{
cur->next = l2;
cur = l2;
l2 = l2->next;
}
}
return ret;
}
};