[C语言][LeetCode][21]Merge Two Sorted Lists

题目

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.

标签

Linked List

难度

简单

分析

题目意思是合并两个排好序的链表，并返回新的链表。解题思路是先找到链表的头，如果L1的第一个元素比较小，新链表的头结点就指向L1，如果L2的第一个元素比较小，新链表的头结点就指向L2。剩下的就是逐个比较剩余L1和L2里的元素。需要注意的是，最后是否比较结束了。

C代码实现

   struct ListNode *head;    struct ListNode *ret;    if(!l1 && l2)        return l2;    if(l1&&!l2)        return l1;    if(!l1 && !l2)        return NULL;    if(l1->val <= l2->val)    {        head = l1;        l1 = l1->next;    }    else    {        head = l2;        l2 = l2->next;    }    ret = head;    while(l1 && l2)    {        if(l1->val < l2->val)        {            head->next = l1;            l1 = l1->next;        }        else        {            head->next = l2;            l2 = l2->next;        }        head->next->next = NULL;        head = head->next;            }    if(l1)        head->next = l1;    else if(l2)        head->next = l2;    return ret;