LeetCode 21. Merge Two Sorted Lists

问题描述:

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.

简单的链表操作。

/**
* 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 && l2 == NULL)return NULL;
        if(l1 == NULL)return l2;
        if(l2 == NULL)return l1;
        ListNode *head = new ListNode(0), *l1Node = l1, *l2Node = l2, *p = head;
        while(l1Node || l2Node){
            if(!l1Node){
                p->next = l2Node;
                break;
            }
            else if(!l2Node){
                p->next = l1Node;
                break;
            }
            else{
                if(l1Node->val < l2Node->val){
                    p->next = l1Node;
                    l1Node = l1Node->next;
                }
                else{
                    p->next = l2Node;
                    l2Node = l2Node->next;
                }
            }
            p = p->next;
        }
        return head->next;
    }
};