【leetcode每日一题】NO21.Merge Two Sorted Lists

淡淡的烟草味﹌ 2022-08-03 15:54 165阅读 0赞

题目：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.

解析：与有序数组合并类似，先声明一个指针，指向值小的头结点，再遍历两个指针，依次比较大小。

代码：

/**
     * 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 *result,*curNode;
            if(l1->val<l2->val)
            {
                result=curNode=l1;
                l1=l1->next;
            }
            else
            {
                result=curNode=l2;
                l2=l2->next;
            }
            while(l1!=NULL&&l2!=NULL)
            {
                if(l1->val<l2->val)
                {
                    curNode->next=l1;
                    l1=l1->next;
                    curNode=curNode->next;
                }
                else
                {
                    curNode->next=l2;
                    l2=l2->next;
                    curNode=curNode->next;
                }
            }
            while(l1!=NULL)
            {
                curNode->next=l1;
                l1=l1->next;
                curNode=curNode->next;
            }
            while(l2!=NULL)
            {
                curNode->next=l2;
                l2=l2->next;
                curNode=curNode->next;
            }
            return result;
        }
    };