实验内容：

１．利用尾插法建立一个双向链表。
２．遍历双向链表。
３．实现双向链表中删除一个指定元素。
４．在非递减有序双向链表中实现插入元素e仍有序的算法。
５．判断双向链表中元素是否对称，若对称返回 1，否则返回 0。
６．设元素为正整型，实现算法把所有奇数排列在偶数之前。
７．在主函数中设计一个简单菜单，调用上述算法。

实验说明：

双向链表的类型定义

   typedef  int  ElemType；  // 元素类型 
   typedef  struct  DuLNode 
   {
ElemType  data; 
      DuLNode *prior, *next; 
   } DuLNode, *pDuLinkList;  

源代码

#include <iostream>
#include <time.h>
#include <stdlib.h>
#include <iomanip>
using namespace std;

typedef  int  ElemType;
typedef  struct  DuLNode
{
    ElemType  data;
    struct DuLNode *prior, *next;
} DuLNode, *pDuLinkList;

pDuLinkList DuLinkLinst_Init()         //建立双向链表
{
    int n;
    DuLNode *phead, *tmp, *p;
    srand(unsigned(time(NULL)));
    cout << "输入建立链表的元素个数：";
    cin >> n;
    phead = new DuLNode;
    phead->next = phead;
    phead->prior = phead;
    p = phead;
    for (int i = 0; i < n; i++)
    {
        tmp = new DuLNode;
        tmp->data = rand() % 100;
        tmp->prior = p;
        p->next = tmp;
        p = tmp;
    }
    p->next = phead;
    phead->prior = p;
    return phead;
}
void DuLinkList_Display(pDuLinkList phead)   //输出双向链表
{
    DuLNode *p;
    p = phead->next;
    while (p != phead)
    {
        cout << setw(4) << p->data;
        p = p->next;
    }
    cout << endl;
}
void DuLinkList_Free(pDuLinkList phead)   //释放双链表
{
    DuLNode *p, *t;
    p = phead->next;
    while (p != phead)
    {
        t = p;
        p = p->next;
        delete t;
    }
    delete p;
}
void DuLinkList_Del(pDuLinkList phead, ElemType x)    //删除指定元素
{
    DuLNode *p1, *p2;
    p1 = phead->next;
    p2 = phead;
    while (p1)
    {
        if (x == p1->data)
        {
            p2->next = p1->next;
            p1->next->prior = p2;
            delete p1;
            return;
        }
        p2 = p1;
        p1 = p1->next;
    }
    cout << "指定元素未找到！" << endl;
}
void DuLinkList_Sort(pDuLinkList phead)               //排序
{
    DuLNode *p;
    int count = 0, i = 0;
    ElemType *num, tmp;
    p = phead->next;
    if (p == phead)
    {
        cout << "双向链表为空！" << endl;
        return;
    }
    while (p != phead)
    {
        count++;
        p = p->next;
    }
    num = new ElemType[count];
    p = phead->next;
    while (p != phead)
    {
        num[i++] = p->data;
        p = p->next;
    }
    for (int k = 0; k < count - 1; k++)
        for (int j = 0; j < count - k - 1; j++)
            if (num[j] > num[j + 1])
            {
                tmp = num[j];
                num[j] = num[j + 1];
                num[j + 1] = tmp;
            }
    p = phead->next;
    i = 0;
    while (p != phead)
    {
        p->data = num[i++];
        p = p->next;
    }
    delete[] num;
}
void DuLinkList_Insert(pDuLinkList phead, ElemType elem)    //插入一个元素
{
    DuLNode *p, *tmp;
    p = phead->next;

    while (p != phead)
    {
        if (elem <= p->data)
            break;
        p = p->next;
    }
    tmp = new DuLNode;
    tmp->data = elem;
    tmp->next = p;
    tmp->prior = p->prior;
    p->prior->next = tmp;
    p->prior = tmp;
}
int DuLinkList_symmetry(pDuLinkList phead)  //链表中元素是否对称
{
    DuLNode *p1, *p2;
    p1 = phead->prior;
    p2 = phead->next;
    while (p1 != p2)
    {
        if (p1->data != p2->data)
        {
            return 0;
        }
        p1 = p1->prior;
        p2 = p2->next;
    }
    return 1;
}
void DuLinkList_jiousort(pDuLinkList phead)     //奇数在偶数前面
{
    DuLNode *p1, *p2;
    p1 = phead->next;
    p2 = p1->next;
    if (p1 == phead)
    {
        cout << "双向链表为空！" << endl;
        return;
    }
    if (p2 == phead)
    {
        return;
    }
    while (p1 != phead)
    {
        if ((p1->data) % 2 != 0)
        {
            p2 = p1;
            p1 = p1->next;

            p1->prior = p2->prior;
            p2->prior->next = p1;

            p2->next = phead->next;
            phead->next->prior = p2;
            phead->next = p2;
            p2->prior = phead;
        }
        else
            p1 = p1->next;
    }
}
int main()
{
    DuLNode *L = NULL;
    ElemType t;
    int num;
    cout << "1:利用尾插法建立一个双向链表" << endl;
    cout << "2:遍历双向链表" << endl;
    cout << "3:双向链表中删除一个指定元素" << endl;
    cout << "4:在非递减有序双向链表中实现插入元素e仍有序的算法。" << endl;
    cout << "5:判断双向链表中元素是否对称，若对称返回 1，否则返回 0" << endl;
    cout << "6:设元素为正整型，实现算法把所有奇数排列在偶数之前" << endl;
    cout << "7:退出" << endl;
    while (true)
    {
        cout << "请输入一个数字选项:";
        cin >> num;
        switch (num)
        {
        case 1:
        {
            L = DuLinkLinst_Init();
            cout << "L双向链表为：";
            DuLinkList_Display(L);
            cout << endl;
        }break;
        case 2:
        {
            cout << "双向链表为：";
            DuLinkList_Display(L);
            cout << endl;
        }break;
        case 3:
        {
            cout << "输入需要删除的元素：";
            cin >> t;
            DuLinkList_Del(L, t);
            cout << "双向链表为：";
            DuLinkList_Display(L);
            cout << endl;
        }break;
        case 4:
        {
            cout << "输入要插入的元素：";
            cin >> t;
            DuLinkList_Sort(L);
            DuLinkList_Insert(L, t);
            cout << "双向链表为：";
            DuLinkList_Display(L);
            cout << endl;
        }break;
        case 5:
        {
             if(DuLinkList_symmetry(L)==1)
                 cout << "双向链表中元素对称" << endl;
             else 
                 cout << "双向链表中元素不对称" << endl;
             cout << endl;
        }break;
        case 6:
        {
            DuLinkList_jiousort(L);
            cout << "双向链表为：";
            DuLinkList_Display(L);
            cout << endl;
        }break;
        case 7:
        {
            DuLinkList_Free(L);
            cout << endl;
            return 0;
        }break;
        default:
            cout << "输入错误！请重新输入！" << endl;
            cout << endl;
        }
    }
    return 0;
}

运行截图：

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