[Leetcode] Merge k Sorted Lists

最新推荐文章于 2024-04-03 21:24:25 发布

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本文介绍了一种高效的算法来合并多个已排序的链表。通过定义一个Solution类，该类包含两个主要方法：mergeKLists用于合并K个排序链表；mergeTwoList则负责合并两个链表。此算法采用迭代方式，逐步将每个链表两两合并，直至所有链表完全合并为一个有序链表。

/**
 * 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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
        if (lists.size() == 0) return NULL;
        
        ListNode* res = lists[0];
        for (int i = 1; i < lists.size(); ++i)
        {
            res = mergeTwoList(res, lists[i]);
        }
        
        return res;
    }
    
    ListNode* mergeTwoList(ListNode* l1, ListNode* l2)
    {
        ListNode* res = NULL;
        ListNode** pp = &res;
        
        ListNode* cur1 = l1;
        ListNode* cur2 = l2;
        while (cur1 && cur2)
        {
            if (cur1->val < cur2->val)
            {
                *pp = cur1;
                pp = &(cur1->next);
                cur1 = cur1->next;
            }
            else
            {
                *pp = cur2;
                pp = &(cur2->next);
                cur2 = cur2->next;
            }
        }
        
        if (cur1)
            *pp = cur1;
        else
            *pp = cur2;
            
        return res;
    }
};