leetcode-21 Merge Two Sorted Lists

題意: 合併兩個已經排序好的linked list

解法: 面對linked list題目時,為了方便處理,都可以自己先創造一個原點(ori),最後再回傳ori->next即可

程式碼如下:

/**
 * 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* ori= new ListNode(0);
        ListNode* head=ori;
        while(l1!=NULL||l2!=NULL)
        {
             if(l1==NULL)
             {
                head->next=l2;
                break;
             }
             if(l2==NULL)
             {
                head->next=l1;
                break;
             }
            if(l1->val<l2->val)
            {
                head->next=l1;
                l1=l1->next;
                head=head->next;
            }
            else
            {
                 head->next=l2;
                 l2=l2->next;
                 head=head->next;
            }
        }
        return ori->next;
    }
};