/**
* 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* an = new ListNode(0);
ListNode* ans = an;
if(l1==NULL && l2==NULL) return NULL;
while(l1 != NULL || l2 != NULL){
if( l2==NULL|| ( l1!=NULL&& (l1->val < l2->val)) ){
ans->next = l1;
ans = ans->next;
l1 = l1->next;
continue;
}
if( l1==NULL || (l2!=NULL&&(l2->val <= l1->val))){
ans->next = l2;
ans = ans->next;
l2 = l2->next;
continue;
}
}
return an->next;
}
};
注意這個或條件的順序,否則LeetCode會報錯,說可能存在調用空指針隐患