大家好我试图使用互联网上发现的alghoritm在我的调度程序代码中构建quicksort。我的问题是,在代码的某些时候,我得到了关于getPrev的访问冲突,可能它指向null但是我被卡住了,并且不知道如何让它工作。感谢任何一点帮助,或者至少建议我去哪个方向。我已经花了几个小时,它没有任何效果。
#include <iostream>
using namespace std;
class Node
{
public:
Node(int value, Node* nextptr = nullptr, Node* prevptr = nullptr, int currentpriority = 0)
{
this->value = value;
next = nextptr;
prev = prevptr;
priority = currentpriority;
}
int getVal(void)
{
return value;
}
Node* getNext(void)
{
return next;
}
Node* getPrev(void)
{
return prev;
}
void setVal(int value)
{
this->value = value;
}
void setPrev(Node* prevptr)
{
prev = prevptr;
};
void setNext(Node* nextptr)
{
next = nextptr;
}
int getPriority(void)
{
return priority;
}
void setPriority(int priority)
{
this->priority = priority;
}
private:
Node* next;
Node* prev;
int priority;
int value;
};
class Stack
{
public:
Stack(void)
{
top = nullptr;
}
~Stack(void)
{
while (NodePop() != nullptr);
}
void Push(int value)
{
Node* tmp = new Node(value, top);
top = tmp;
}
Node* NodePop(void)
{
Node* tmp = top;
if (top != nullptr) top = top->getNext();
return tmp;
}
int Pop(void)
{
Node* tmp = NodePop();
int ret = 0;
if (tmp != nullptr)
{
ret = tmp->getVal();
}
else
{
throw "Stack Empty";
}
delete tmp;
return ret;
}
private:
Node* top;
};
class Queue
{
public:
Queue(void)
{
back = front = nullptr;
}
~Queue(void)
{
while (NodeDequeue() != nullptr);
}
void Enqueue(int i, int priority = 0)
{
Node* tmp = new Node(i, back, nullptr, priority);
back = tmp;
if (front == nullptr) front = back;
else
{
tmp = back->getNext();
tmp->setPrev(back);
}
}
int Dequeue(void)
{
Node* tmp = NodeDequeue();
int ret = 0;
if (tmp != nullptr)
{
ret = tmp->getVal();
}
else
{
throw "Queue Empty";
}
if (front == nullptr) back = front; // queue now empty
delete tmp;
return ret;
}
protected:
Node* back;
Node* front;
private:
virtual Node* NodeDequeue(void)
{
Node* tmp = front;
if (front != nullptr)
{
front = front->getPrev();
if (front != nullptr) front->setNext(nullptr);
}
return tmp;
}
};
class Scheduler : public Queue
{
public:
Node*getTail_Dll(Node*Head)
{
if (Head != NULL)
{
while (Head->getNext() != NULL)
Head = Head->getNext();
}
return Head;
}
void partition_QuickSort_Dll(Node*Head, Node*Tail)
{
Node* NewTail=NULL,*Curr = Head, *Pivot = Tail;
while (Curr != Pivot)
{
if ((Curr->getVal()) > (Pivot->getVal()))
{
if (Curr->getPrev() != NULL)
Curr->getPrev()->setNext(Curr->getNext());
if (Curr->getNext() != NULL)
Curr->getNext()->setPrev(Curr->getPrev());
NewTail = Curr;
Curr = Curr->getNext();
if (Curr->getPrev() == NULL)
Head = Curr;
NewTail->setPrev(Tail);
NewTail->setNext(NULL);
Tail->setNext( NewTail);
}
else
Curr = Curr->getNext();
}
if (Pivot->getPrev() != NULL)
Pivot->getPrev()->setNext(NULL);
if (Pivot->getNext() != NULL)
Pivot->getNext()->setPrev(NULL);
}
void quickSortList_Recur_Dll(Node*Head, Node*Tail)
{
Node*Pivot = Tail;
if ((Head != NULL) && (Tail != NULL) && (Head != Tail))
{
/* partition */
partition_QuickSort_Dll(Head, Tail);
/* sort left part */
quickSortList_Recur_Dll(Head, (Pivot->getPrev()));
/* sort right part */
quickSortList_Recur_Dll(Pivot->getNext(), Tail);
/* connect pivot to left & right parts */
if (Pivot->getPrev() != NULL)
Pivot->getPrev()->setNext(Pivot);
if (Pivot->getNext() != NULL)
Pivot->getNext()->setPrev( Pivot);
}
}
void quickSortList_Dll(Node*Head)
{
Node*Tail = getTail_Dll(Head);
if (Head != NULL)
quickSortList_Recur_Dll(Head, Tail);
}
/*Node* split()
{
Node *singleJump = back, *doubleJump = back;
while (singleJump->getNext() && doubleJump->getNext()->getNext())
{
doubleJump = doubleJump->getNext()->getNext();
singleJump = singleJump->getNext();
}
Node *temp = singleJump->getNext();
singleJump->getNext()->setNext(nullptr);
return temp;
}
*/
/*void antiBlock()
{
cycle++;
if (cycle == 5)
{
Node* temp = split();
while (temp != front)
{
if (temp->getPriority() < 10)
temp->setPriority(temp->getPriority() + 1);
}
cycle = 0;
}
}*/
Node* NodeDequeue(void)
{
Node* tmp = front;
//antiBlock();
quickSortList_Dll(back);
if (front != nullptr)
{
front = front->getPrev();
if (front != nullptr) front->setNext(nullptr);
}
return tmp;
}
};
int main()
{
Scheduler* s = new Scheduler;
s->Enqueue(11, 5);
s->Enqueue(2, 6);
s->Enqueue(3, 1);
s->Enqueue(40, 8);
s->Enqueue(15, 9);
s->Enqueue(6, 10);
//s->Enqueue(67, 6);
//s->Enqueue(78, 3);
//s->Enqueue(529, 2);
//s->Enqueue(110, 7);
//s->Enqueue(211, 4);
//s->Enqueue(312, 8);
//s->Enqueue(413, 3);
//s->Enqueue(154, 6);
//s->Enqueue(135, 2);
//s->Enqueue(116, 7);
for (int i = 0; i < 6; i++)
cout << s->Dequeue() << endl;
return 0;
};
答案 0 :(得分:0)
您是否需要使用quicksort(不是列表&#34;友好&#34;)?如果没有,请使用自下而上的合并排序与指向列表的第一个节点的指针数组。它是一种旧算法,但出于某种原因,它并不为人所知。它只使用前向(下一个)指针和合并两个已经排序的列表的典型MergeLists(),因此它的列表&#34;友好&#34;。
示例模式,第一个节点存储在数组[0]中。第二个节点与array [0]合并以创建一个大小为2的列表并存储在array [1]中(array [0]被清除)。两个节点之后,大小为2的列表与array [1]合并以创建大小为4的列表并存储在array [2](array [0],array [1]已清除)中。 array [30]包含一个大小为10亿(2 ^ 30)的列表。 array [31]列表大小不受限制,一次合并10亿个节点。因此,32的数组大小是过度的,但是占用的空间很小,你也可以使用它。
维基文章:
http://en.wikipedia.org/wiki/Merge_sort#Bottom-up_implementation_using_lists
答案 1 :(得分:0)
在NodeDequeue
中,我认为您在第一个getPrev
上呼叫Node
。第一个节点之前的节点应始终为null
。如果您要删除第一个节点,则应将first
设置为first->next
,然后将first->prev
设置为null
。