【leetcode】merge-two-sorted-lists

//水题 练手 链表
//2014年8月25日19:17:20
//
#include <iostream>

using namespace std;

struct ListNode {
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};

class Solution {
public:
ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
ListNode root(0);
ListNode *p = &root;
while(l1 != NULL &&l2!=NULL){
if(l1->val < l2->val){
p->next = l1;
p = p->next;
l1 = l1->next;
}
else{
p->next = l2;
p = p->next;
l2 = l2 -> next;
}
}
if(l1 == NULL){
p->next = l2;
}
else {
p->next = l1;
}
return root.next;

}
};
int main()
{
ListNode node1(1);
ListNode node2(3);
ListNode node3(5);
ListNode node4(2);
ListNode node5(4);
ListNode node6(6);

node1.next = &node2;
node2.next = &node3;
node4.next = &node5;
node5.next = &node6;

Solution S;
ListNode * ret = S.mergeTwoLists(&node1,&node4);
while(ret != NULL){
cout << ret->val << " ";
ret = ret->next;
}
cout << endl;

return 0;
}