[LeetCode]Merge k Sorted Lists

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

/**
 * 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.size() == 0)
	{
		return NULL;
	}
	if (lists.size() == 1)
	{
		return lists[0];
	}
	
	int pos = 0;
	int count = 0;

	for (int i = 0; i < lists.size(); i++)
	{
		ListNode* p = lists[i];
		while(p != NULL)
		{
			count++;
			p = p->next;
		}
	}
	if (count > 0)
	{
		ListNode* ans = new ListNode(0);
		ListNode* ansTemp= ans;
		while(count)
		{
			int min = INT_MAX;
			for (int i = 0; i < lists.size(); i++)
			{
				if (lists[i] != NULL)
				{
					if ( (*lists[i]).val < min)
					{
						min = (*lists[i]).val;
						pos = i;
					}
				}
			}
			ansTemp->val = (*lists[pos]).val;
			if (count > 1)
			{
				ansTemp->next = new ListNode(0);
				ansTemp = ansTemp->next;
			}
			lists[pos] = lists[pos]->next;
			count--;
		}
		return ans;
	}
	else
	{
		return lists[0];
	}
    }
};

网上看到使用优先队列做的：

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    struct comp
    {
	//优先队列中默认是less(<),top为最大的元素
	//此处为greater(>),top为最小元素
	bool operator() (ListNode *a,ListNode *b)
	{
		return a->val > b->val;
	}
    };
    ListNode *mergeKLists(vector<ListNode *> &lists)
    {
    ListNode *tmphead = new ListNode(0), *p = tmphead;
	std::priority_queue<ListNode*,  std::vector<ListNode*>,  comp> q;
	for(int i = 0; i < lists.size(); i ++)
	{
		if(lists[i] != NULL)
		{
			q.push(lists[i]);
		}
	}
	while(!q.empty())
	{
		p->next = q.top();
		p = p->next;
		q.pop();
		if(p ->next != NULL)
		{	
			q.push(p->next);
		}
	}
	return tmphead->next;
    }
};

http://blog.csdn.net/jet_yingjia/article/details/26394567

[LeetCode]Merge k Sorted Lists,布布扣,bubuko.com

[LeetCode]Merge k Sorted Lists

标签：des   style   blog   class   c   code   

原文地址：http://blog.csdn.net/jet_yingjia/article/details/26362817