双向链表

#include <bits/stdc++.h>
using namespace std;
typedef int ElemType;
/**
 * 双向链表
 */
typedef struct Node
{
    struct Node *pre;
    ElemType data;
    struct Node *next;
} Node;

void InitList(Node *&L)
{
    L = (Node *)malloc(sizeof(Node));
    L -> pre = NULL;
    L -> next = NULL;
}

int GetLength(Node *L)
{
    int length = 0;
    Node *p = L -> next;
    while(p != NULL)
    {
        length++;
        p = p -> next;
    }
    return length;
}

int GetElem(Node *L, int i, ElemType &e)
{
    Node *p = L -> next;
    if(i < 1 || i > GetLength(L))
        return 0;
    for(int j = 1; j < i; j++)
    {
        p = p -> next;
    }
    e = p -> data;
    return 1;
}

int Lacate(Node *L, ElemType x)
{
    int pos = 1;
    Node *p = L -> next;
    while(p != NULL && p -> data != x)
    {
        p = p -> next;
        pos++;
    }
    if(p == NULL)
        return 0;
    else return pos;
}

int InsertElem(Node *L, ElemType x, int i)
{
    
    Node *p = L, *s;
    if(i < 1 || i > GetLength(L) + 1)
        return 0;

    for(int j = 1; j < i; j++)
    {
        p = p -> next;
    }
    s = (Node *)malloc(sizeof(Node));
    s -> data = x;
    s->next=NULL;
    s->pre =NULL;

    s -> next = p -> next;
    if(p -> next != NULL)
        p -> next -> pre = s;
    p -> next = s;
    s -> pre = p;
    return 1;
}

int DelElem(Node *L, int i)
{
    if(i < 1 || i > GetLength(L))
        return 0;
    Node *p = L, *q;
    for(int j = 1; j < i; j++)
    {
        p = p -> next;
    }
    q = p -> next;
    p -> next = q -> next;
    q -> next -> pre = p;
    free(q);
    return 1;
}

void PrintList(Node *L)
{
    Node *p = L -> next;
    while(p != NULL)
    {
        cout << p -> data << endl;
        p = p -> next;
    }
}

void BackPrintList(Node *L)
{
    Node *p = L;
    for(int j = 1; j <= GetLength(L); j++)
    {
        p = p -> next;
    }
    while(p != NULL)
    {
        if(p -> pre == NULL)
            break;
        cout << p -> data << endl;
        p = p -> pre;
    }
}


int main()
{
    Node *L;
    InitList(L);
    InsertElem(L,1,1);
    InsertElem(L,2,1);
    InsertElem(L,3,1);
    InsertElem(L,4,1);
    InsertElem(L,5,1);
    InsertElem(L,6,1);

    PrintList(L);

    cout << "Reverse output elements:" << endl;
    BackPrintList(L);

    cout << "size:" << GetLength(L) << endl;
    
    DelElem(L,1);
    cout << "After deleting the first element :" << endl;
    PrintList(L);

    cout << "2 in the table position :" << endl;
    cout << Lacate(L,2) << endl;

    ElemType e;
    GetElem(L,1,e);//将第一个元素的值取出
    cout <<"The value of the first element is " << e << endl;
    return 0;
}

好好的，生活还要继续，，，