[LeetCode]23. Merge k Sorted Lists

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于 2018-03-24 08:50:57 发布

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本文链接：https://blog.youkuaiyun.com/Ada_who/article/details/79674660

本文介绍了一种算法，用于合并多个已排序的链表成为一个单一的有序链表。通过递归方式，每次找到当前最小节点并更新链表，直至所有节点被合并。

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

代码如下：

class Solution {
public:
	ListNode* mergeKLists(vector<ListNode*>& lists) {
		if (lists.empty()) return NULL;
		ListNode *front = new ListNode(INT_MAX);
		ListNode *f = front;
		int min = 0, count = 0;
		for (int i=0;i<lists.size();++i)
		{
			if (lists[i]!=NULL&&lists[i]->val < f->val)
			{
				f->val = lists[i]->val;
				min = i;
			}
			if (lists[i] == NULL) ++count;
		}
		if (count == lists.size()) return NULL;
		ListNode *s = lists[min];
		ListNode *r = new ListNode(0);
		if (lists[min]->next != NULL)
		{		
			r->val = lists[min]->next->val;
			r->next = lists[min]->next->next;
			delete s;
		    s = NULL;
			lists[min] = r;
		}
		else
		{
			delete s;
			s = NULL;
			lists[min] = NULL;
			++count;
		}				
		f->next = mergeKLists(lists);
		return front;
	}
};