[leetcode] 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：逐个遍历两条链，较小的拼接到新链后面

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