# 问题 原题链接：[https://leetcode.com/problems/merge-two-sorted-lists/](https://leetcode.com/problems/merge-two-sorted-lists/) 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 ``` # 分析过程 - 输入：两个有序的链表 - 输出：合成一整个链表 - 思路：新建一个根节点，然后按次序扫描两个链表，重新挂接链表。 # 解决方法 ```cpp class Solution { public: ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) { if (!l1 || !l2) { return l1 ?: l2; } ListNode *tmpA = l1, *tmpB = l2; // 新建一个根节点用于往后挂接 ListNode newList = ListNode(0); // 正在挂接的节点 ListNode *tmp = &newList; while (tmpA && tmpB) { if (tmpA->val <= tmpB->val) { tmp->next = tmpA; tmpA = tmpA->next; } else { tmp->next = tmpB; tmpB = tmpB->next; } tmp = tmp->next; } // 其中一个链表空了，此时把另一个挂上去 tmp->next = tmpA ?: tmpB; return newList.next; } }; ```