leetcode/23.cpp at master · zxth93/leetcode · GitHub

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//
//  23.cpp
//  leetcode
//
//  Created by R Z on 2018/2/4.
//  Copyright © 2018年 R Z. All rights reserved.
//

#include <stdio.h>
#include <vector>
using namespace std;
/**
 * Definition for singly-linked list.*/
 struct ListNode {
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
 };
class Solution {
public:
    ListNode* mergeKLists(vector<ListNode*>& lists) {
        if(lists.empty()) return nullptr;
        while(lists.size()>1){
            lists.push_back(mergeTwoLists(lists[0],lists[1]));
            lists.erase(lists.begin());
            lists.erase(lists.begin());
        }
        return lists[0];
    }

    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2){
        if(l1==NULL) return l2;
        if(l2==NULL) return l1;
        if(l1->val<l2->val){
            l1->next=mergeTwoLists(l1->next, l2);
            return l1;
        }else{
            l2->next=mergeTwoLists(l1,l2->next);
            return l2;
        }
    }
};