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  • 合并K个升序链表

    题目链接:
    https://leetcode-cn.com/problems/merge-k-sorted-lists/
    题目描述:
    给你一个链表数组,每个链表都已经按升序排列。
    请你将所有链表合并到一个升序链表中,返回合并后的链表。

    题解:
    归并法,分而治之的思想。

    
    /**
     * Definition for singly-linked list.
     * struct ListNode {
     *     int val;
     *     ListNode *next;
     *     ListNode() : val(0), next(nullptr) {}
     *     ListNode(int x) : val(x), next(nullptr) {}
     *     ListNode(int x, ListNode *next) : val(x), next(next) {}
     * };
     */
    class Solution {
    public:
    
    
        //链表两两合并
        ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
            ListNode *L = new ListNode(-1);
            ListNode *p = L;
            while(l1 != nullptr && l2 != nullptr)
            {
                if(l1->val < l2->val)
                {
                    p->next = l1;
                    l1 = l1->next;
                }else
                {
                    p->next = l2;
                    l2 = l2->next;
                }
                p = p->next;
            }
            p->next = l1 == nullptr ? l2 :l1;
            return L->next;
        }  
    
        ListNode* merge(vector<ListNode*>& lists, int left, int right)
        {
            if(left == right)
                return lists[left];
            int mid = left + (right - left) / 2;
            ListNode* l1 = merge(lists, left, mid);
            ListNode* l2 = merge(lists, mid + 1, right);
            return mergeTwoLists(l1, l2);
        }
    
        ListNode* mergeKLists(vector<ListNode*>& lists) {
            if(lists.size() == 0)
                return nullptr;
            return merge(lists, 0, lists.size() - 1); 
        }
    };
    
    
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  • 原文地址:https://www.cnblogs.com/ZigHello/p/14980764.html
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