合并k个排序链表-LintCode

#ifndef C104_H
#define C104_H
#include<iostream>
#include<vector>
using namespace std;
class ListNode{
public:
int val;
ListNode *next;
ListNode(int val){
this->val = val;
this->next = NULL;
}
};
class Solution {
public:
/**
* @param lists: a list of ListNode
* @return: The head of one sorted list.
*/
ListNode *mergeKLists(vector<ListNode *> &lists) {
// write your code here
int len = lists.size();
for (int i = 0; i < len - 1; ++i)
{
lists[i + 1] = merge(lists[i], lists[i + 1]);
}
return lists[len - 1];
}
ListNode *merge(ListNode *head1, ListNode *head2)
{
ListNode *p = head1, *q = head2;
ListNode *node = new ListNode(0);
ListNode *pn = node;
while (p != NULL||q != NULL)
{
if (p != NULL&&q != NULL)
{
if (p->val <= q->val)
{
pn->next = p;
pn = pn->next;
p = p->next;
}
else
{
pn->next = q;
pn = pn->next;
q = q->next;
}
}
else if (p != NULL&&q == NULL)
{
pn->next = p;
pn = pn->next;
p = p->next;
}
else
{
pn->next = q;
pn = pn->next;
q = q->next;
}
}
return node->next;
}
};
#endif

#include"c104.h"
int main()
{
ListNode *p1 = new ListNode(2);
p1->next = new ListNode(4);
ListNode *p2 = new ListNode(3);
p2->next = new ListNode(5);
ListNode *p3 = new ListNode(6);
p3->next = new ListNode(7);
ListNode *p4 = new ListNode(1);
p4->next = new ListNode(10);
vector<ListNode*> v;
v.push_back(p1);
v.push_back(p2);
v.push_back(p3);
v.push_back(p4);
Solution s;
ListNode *p = s.mergeKLists(v);
while (p != NULL)
{
cout << p->val << " ";
p = p->next;
}
cout << endl;
return 0;
}