链表访问越界

[axiqia]

代码如下：用来计算高精度PI
问题：Codeblocks运行正常，正常输入输出，VS2010报错，PI.exe 中的 0x01371646 处最可能的异常: 0xC0000005: 读取位置 0xcdcdcdcd 时发生访问冲突
我自己的想法：双向列表头和尾我利用同一个节点来保存，且头尾不保存数据，那么tail的pre当是第一个有效节点，且在while中循环条件是pre非空，应该不会出现没有初始化的错误，但是VS还是有错误。还请指正。

#include <iostream>
#include <string.h>
#include <cstdio>
#include <stdlib.h>

using namespace std;
struct Node
{
	int data;
	struct Node *next;
	struct Node *pre;
};
typedef struct Node Node, *PNode;
struct FrontNode
{
	PNode head;
	PNode tail;
};
typedef FrontNode DuLink, *PDuLink;
/******************************/
/*			   建立           */
/******************************/

void CreateList(DuLink *h)
{

	h->head = h->tail = (PNode)malloc(sizeof(Node));
	h->head->data = 0;

	PNode p = h->head;
    for(int i = 0; i < 600; i++)
    {
        PNode q;
        q = (PNode)malloc(sizeof(Node));
        q->data = 0;

        p->next = q;
        q->pre = p;
        p = q;
    }
    h->tail = p;
}

int main()
{
    DuLink sum;
    CreateList(&sum);
    DuLink rn;
    CreateList(&rn);

//    rn.tail->pre->data = 2;
//    sum.tail->pre->data = 1;
    rn.head->next->data = 2;
    sum.head->next->data = 2;
    for(int n = 1; n < 2000; n++)
    {
        PNode p = rn.tail->pre, q;
        int ret = 0;
        while(p!=NULL)
        {
            int temp = (p->data*n+ret);
            //cout << temp << endl;
            p->data = temp%10;
            ret = temp/10;
            p = p->pre;
        }
        //cout << "乘法" << endl;
        p = rn.head->next;
        ret = 0;
        while(p)
        {
            int temp = p->data+ret*10;
            p->data = temp/(2*n+1);
            ret = temp%(2*n+1);
            p = p->next;
        }
        //cout << "除法" << endl;
        p = rn.tail->pre;
        q = sum.tail->pre;
        ret = 0;
        while(q)
        {
            int temp = p->data + q->data + ret;
            q->data = temp%10;
            ret = temp/10;
            p = p->pre;
            q = q->pre;
        }
        //cout << "加法" << endl;
    }
    PNode p = sum.head->next;
    int k;
    cin >> k;
    int cnt = 0;
    while(cnt <= k)
    {
        if(cnt == 0)
            cout << p->data << ".";
        else
            cout << p->data;
        p = p->next;
        cnt++;
    }
    cout << endl;
}

[fefe82]

head->pre 与 tail->next 没有赋值。

[axiqia]

引用 1 楼 fefe82 的回复:

head->pre 与 tail->next 没有赋值。

引用 1 楼 fefe82 的回复:

head->pre 与 tail->next 没有赋值。

谢谢，已解决

[axiqia]

附代码

#include <iostream>
#include <string.h>
#include <cstdio>
#include <stdlib.h>

using namespace std;
struct Node
{
	int data;
	struct Node *next;
	struct Node *pre;
};
typedef struct Node Node, *PNode;
struct FrontNode
{
	PNode head;
	PNode tail;
};
typedef FrontNode DuLink, *PDuLink;
/******************************/
/*			   建立           */
/******************************/

void CreateList(DuLink *h)
{

	h->head = (PNode)malloc(sizeof(Node));
	h->tail = (PNode)malloc(sizeof(Node));
	h->head->pre = NULL;
	h->head->next = NULL;
	h->tail->pre = NULL;
	h->tail->next = NULL;
	h->head->data = 0;

	PNode p = h->head;
    for(int i = 0; i < 600; i++)
    {
        PNode q;
        q = (PNode)malloc(sizeof(Node));
        q->data = 0;

        p->next = q;
        q->pre = p;
        p = q;
    }
    h->tail = p;
}

int main()
{
    DuLink sum;
    CreateList(&sum);
    DuLink rn;
    CreateList(&rn);

//    rn.tail->pre->data = 2;
//    sum.tail->pre->data = 1;
    rn.head->next->data = 2;
    sum.head->next->data = 2;
    for(int n = 1; n < 2000; n++)
    {
        PNode p = rn.tail->pre, q;
        int ret = 0;
        while(p!=rn.head)
        {
            int temp = (p->data*n+ret);
            //cout << temp << endl;
            p->data = temp%10;
            ret = temp/10;
            p = p->pre;
        }
        //cout << "乘法" << endl;
        p = rn.head->next;
        ret = 0;
        while(p!=rn.tail)
		{
            int temp = p->data+ret*10;
            p->data = temp/(2*n+1);
            ret = temp%(2*n+1);
            p = p->next;
        }
        //cout << "除法" << endl;
        p = rn.tail->pre;
        q = sum.tail->pre;
        ret = 0;
        while(q!=sum.head)
        {
            int temp = p->data + q->data + ret;
            q->data = temp%10;
            ret = temp/10;
            p = p->pre;
            q = q->pre;
        }
        //cout << "加法" << endl;
    }
    PNode p = sum.head->next;
    int k;
    cin >> k;
    int cnt = 0;
    while(cnt <= k)
    {
        if(cnt == 0)
            cout << p->data << ".";
        else
            cout << p->data;
        p = p->next;
        cnt++;
    }
    cout << endl;
}