題目

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.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

題意

輸入兩個已經排好序的連結串列，輸出按順序合併成的新連結串列。 

分析

*if (l1 && (!l2 || l1->val < l2->val))

程式碼

/**
 * 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 pre = ListNode(0), *l = ⪯
        while (l1 || l2){
            if (l1 && (!l2 || l1->val < l2->val)){
                l->next = l1;
                l1 = l1->next;
            }else{
                l->next = l2;
                l2 = l2->next;
            }
            l = l->next;
        }
        return pre.next;
    }
};