LeetCode 21. Merge Two Sorted Lists

LeetCode 21. Merge Two Sorted Lists

Solution1：我的答案
yeah~yeah~yeah~

/**
 * 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) {
        if (!l1 && !l2) return NULL;
        else if (!l1) return l2;
        else if (!l2) return l1;
        ListNode* new_head = new ListNode(-1);
        ListNode* cur = new_head;
        while (l1 && l2) { //l1,l2必须都不能为空
            if (l1->val <= l2->val) {
                cur->next = l1;
                l1 = l1->next;
                cur = cur->next;
                cur->next = NULL;
            } else {
                cur->next = l2;
                l2 = l2->next;
                cur = cur->next;
                cur->next = NULL;
            }
        }
        if (l1) cur->next = l1;
        if (l2) cur->next = l2;
        return new_head->next;
    }
};