[各种面试题] 链表快排

前面写了个链表的归并排序，这里再写个链表的快排。

链表的快排处理其实跟数组的没什么区别，只是在partition要三位取中的话稍微烦一点；

#include<iostream>
#include<vector>
#include<ctime>
using namespace std;
struct ListNode
{
	int val;
	ListNode* next;
};

typedef ListNode LN;
LN* getLast(LN* head)
{
	LN* last=head;
	while(head)
	{
		last=head;
		head=head->next;
	}
	return last;
}

LN* partition(LN* head,LN*& lHead,LN*& lTail,LN*& rHead,LN*& rTail)
{
	if ( !head || head->next==NULL)
		return head;
	LN small,*sTail=&small;
	LN big,*bTail=&big;
	LN* piv=head;
	head=head->next;
	piv->next=NULL;
	while(head)
	{
		if ( head->val<= piv->val)
		{
			sTail->next=head;
			sTail=head;
		}
		else
		{
			bTail->next=head;
			bTail=head;
		}
		head=head->next;
	}
	bTail->next=sTail->next=NULL;
	lHead=small.next;
	if (lHead )
		lTail=sTail;
	rHead=big.next;
	if (rHead )
		rTail=bTail;
	return piv;
}

void quickSort(LN*& head,LN*& tail)
{
	if (head==NULL||head==tail)
		return;
	LN* lHead=NULL,*lTail=NULL;
	LN* rHead=NULL,*rTail=NULL;
	LN* piv=partition(head,lHead,lTail,rHead,rTail);
	quickSort(lHead,lTail);
	quickSort(rHead,rTail);
	LN guard;
	tail=&guard;
	if ( lHead )
	{
		tail->next=lHead;
		tail=lTail;
	}
	tail->next=piv;
	tail=piv;
	if ( rHead )
	{
		tail->next=rHead;
		tail=rTail;
	}
	head=guard.next;
}
LN* sortList(LN* list)
{
	if ( !list || list->next==NULL)
		return list;
	LN* last=getLast(list);
	quickSort(list,last);
	return list;
}
int main()
{
	int n;
	while(cin>>n)
	{
		srand( (unsigned)time( NULL ) );
		vector<ListNode> lists(n);
		for(int i=0;i<n;i++)
		{
			lists[i].val=(rand()%100);
		}
		for(int i=0;i<n-1;i++)
			lists[i].next=&lists[i+1];
		lists[n-1].next=NULL;
		ListNode* head=sortList(&lists[0]);
		cout << 1 <<endl;
	}
}