[leetcode] 21. Merge Two Sorted Lists

题目链接：https://leetcode.com/problems/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.

思路

建立一个虚头结点, 然后每次取两个结点中比较小的即可.

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