学步园

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.

思路：

没什么好想的。

题解：

/**
 * 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) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        ListNode* newhead = new ListNode(0);
        ListNode* newlast = newhead;
        
        auto push = [&] (ListNode* node){
            newlast->next = node;
            newlast = node;
        };
        
        ListNode* il1 = l1;
        ListNode* il2 = l2;
        
        while(il1 !=  nullptr && il2 != nullptr)
        {
            if (il1->val > il2->val)
            {
                push(il2);
                il2 = il2->next;
            }
            else
            {
                push(il1);
                il1 = il1->next;
            }
        }
        
        if (il1 == nullptr)
            newlast->next = il2;
        else
            newlast->next = il1;
        
        newlast = newhead->next;
        delete newhead;
        return newlast;
    }
};