LeetCode——Merge Two Sorted Lists

最新推荐文章于 2025-09-11 19:19:55 发布

pickless

最新推荐文章于 2025-09-11 19:19:55 发布

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分类专栏： Online Judge 文章标签： leetcode

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本文介绍了一种合并两个已排序链表的方法，并提供了一个C++实现示例。该方法通过比较两个链表节点的值来合并链表，最终返回一个新的有序链表。

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.

» Solve this problem

/**
 * 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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (l1 == NULL || l2 == NULL) {
            return l1 == NULL ? l2 : l1;
        }
        ListNode *head = NULL, *prev = NULL, *ptr = NULL;
        while (l1 != NULL && l2 != NULL) {
            ptr = l1->val < l2->val ? l1 : l2;
            if (prev != NULL) {
                prev->next = ptr;                
            }
            if (head == NULL) {
                head = ptr;
            }
            prev = ptr;
            l1 = l1 == ptr ? l1->next : l1;
            l2 = l2 == ptr ? l2->next : l2;
            ptr->next = NULL;
        }
        prev->next = l1 != NULL ? l1 : l2;
        return head;
    }
};