21-merge-two-sorted-lists.md

21. Merge Two Sorted Lists - 合并两个有序链表

将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。 

示例：

输入：1->2->4, 1->3->4
输出：1->1->2->3->4->4

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题目标签：Linked List

题目链接：LeetCode / LeetCode中国

题解

Language	Runtime	Memory
cpp	12 ms	1.9 MB

/**
 * 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* res = new ListNode(-1);
        ListNode* r = res;
        ListNode* p = l1;
        ListNode* q = l2;
        while (p && q) {
            if (p->val < q->val) {
                r->next = new ListNode(p->val);
                p = p->next;
            } else {
                r->next = new ListNode(q->val);
                q = q->next;
            }
            r = r->next;
        }
        while (p) {
            r->next = new ListNode(p->val);
            p = p->next;
            r = r->next;
        }
        while (q) {
            r->next = new ListNode(q->val);
            q = q->next;
            r = r->next;
        }
        res = res->next;
        return res;
    }
};