Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.（合并两个已排序的链接列表并将其作为新列表返回。新列表应该通过拼接前两个列表的节点来完成。）
Example:
Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4
/**
* 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 *newNode = new ListNode(-1);
ListNode *pNode = newNode;
while (l1 && l2) {
if (l1->val > l2->val) {
pNode->next = l2;
pNode = l2;
l2 = l2->next;
}
else {
pNode->next = l1;
pNode = l1;
l1 = l1->next;
}
}
if (l1) pNode->next = l1;
if (l2) pNode->next = l2;
pNode = newNode->next;
delete newNode;
return pNode;
}
};
参考链接：
