LeetCode 21. Merge Two Sorted Lists

描述

解决

/**
* 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) {
char buf[sizeof(ListNode)];
ListNode* ptrHead = new(buf) ListNode(-1);
ListNode* tmp = nullptr;
if (l1 == NULL && l2 == NULL)
return NULL;
else if (l1 == NULL)
return l2;
else if (l2 == NULL)
return l1;
if (l1 -> val > l2 -> val){
ptrHead -> next = l2;
tmp = l2;
l2 = l2 ? l2 -> next : NULL;
}else{
ptrHead -> next = l1;
tmp = l1;
l1 = l1 ? l1 -> next : NULL;
}
while (l1 || l2){
if (l1 == NULL){
tmp -> next = l2;
tmp = l2;
l2 = l2 -> next;
break;
}else if (l2 == NULL){
tmp -> next = l1;
tmp = l1;
l1 = l1 -> next;
break;
}else if (l1 -> val > l2 -> val){
tmp -> next = l2;
tmp = l2;
l2 = l2 -> next;
}else{
tmp -> next = l1;
tmp = l1;
l1 =l1 -> next;
}
}
return ptrHead -> next;
}
};