【LeetCode热题100道】21. 合并两个有序链表

class Solution {
public:
    ListNode* mergeTwoLists(ListNode* list1, ListNode* list2) {

        ListNode* root = new ListNode(0);
        ListNode* result = root;
        while(list1 != nullptr && list2 != nullptr)
        {
            if(list1->val > list2->val)
            {
               root->next = list2;
               root = root->next;
               list2 = list2->next;
            }
            else
            {
               root->next = list1;
               root = root->next;
               list1 = list1->next;
            }
        }
        if(list1 != nullptr)
        {
            root->next = list1;
        }
        if(list2 != nullptr)
        {
            root->next = list2;
        }
        return result->next;
    }
};