c_cpp 21.合并两个排序列表 - 难度容易 - 2018.8.10

Posted 2021-05-14

/**
 * 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 == NULL) return l2;
        if (l2 == NULL) return l1;
        
        ListNode *newHead = ListNode(0);
        ListNode *workNode = newHead;
        while (l1 && l2) {
            if (l1->val > l2->val) {
                workNode->next = l2;
                l2 = l2->next;
            } else {
                workNode->next = l1;
                l1 = l1->next;
            }
            workNode = workNode->next;
        }
        
        workNode->next = l1 != NULL ? l1 : l2;

        return newHead->next;
    }
};