leetcode:Merge k Sorted Lists

最新推荐文章于 2025-08-24 21:48:02 发布

转载最新推荐文章于 2025-08-24 21:48:02 发布 · 91 阅读

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原文链接：http://www.cnblogs.com/jzdwajue/p/7193680.html

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#开发工具

本文介绍了一种合并K个已排序链表的有效算法，并详细解释了如何通过迭代地将两个链表合并来逐步减少链表数量，最终得到一个完全排序的链表。此方法简单直观，易于理解和实现。

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Merge k Sorted Lists
Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.

分析
The basic idea is really simple. We can merge first two lists and then push it back. Keep doing this until there is only one list left in vector. Actually, we can regard this as an iterative divide-and-conquer solution.

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