双向链表的实现

#include

using namespace std;

struct DLinkNode{

int data;

DLinkNode* prior;

DLinkNode* next;

};

void Initalize(DLinkNode*& L) { //创建双向链表

L = new DLinkNode;

L->prior = 0;

L->next = 0;

}

void Push_Back(DLinkNode*& L, int x) { //头部插入

DLinkNode* p = L, * A = new DLinkNode;

A->data = x;

while (p->next != 0) {

p = p->next;

}

p->next = A;

A->prior = p;

A->next = 0;

}

void Push_Head(DLinkNode*& L, int x) { //尾部插入

DLinkNode* A = new DLinkNode;

A->data = x;

A->next = L->next;

L->next->prior = A;

L->next = A;

A->prior = L;

}

int Length(DLinkNode* L) { //计算单链表的长度

DLinkNode* p;

p = L->next;

int len = 0;

while (p) {

len++;

p = p->next;

}

return len;

}

DLinkNode* Find(DLinkNode*& L, int i) { //找到第i个元素的地址

if (i<0 || i>Length(L)) return 0;

DLinkNode* p;

p = L;

int j = 0;

while (j < i) {

p = p->next;

j++;

}

return p;

}

void Insert(DLinkNode*& L, int i, int x) { //在第i个位置插入

if (i<0 || i>Length(L) + 1) return;

if (i == Length(L) + 1)

Push_Back(L, x);

else {

DLinkNode* p = Find(L, i - 1);

Push_Head(p, x);

}

}

void Pop_Back(DLinkNode*& L) { //尾部删除

DLinkNode* p;

p = L;

while (p->next != 0) {

p = p->next;

}

p->prior->next = 0;

delete p;

}

void Pop_Head(DLinkNode*& L) { //头部删除

DLinkNode* p;

p = L;

p->next->prior = L;

L = L->next;

delete p;

}

void Delete(DLinkNode*&L,int i) { //删除第i个元素

if (i<0 || i>Length(L)) return;

if (i == 0)

Pop_Head(L);

if (i == Length(L))

Pop_Back(L);

else {

DLinkNode* p = Find(L, i);

p->prior->next = p->next;

p->next->prior = p->prior;

delete p;

}

}

void Print(DLinkNode* L) { //打印链表

DLinkNode* p;

p = L->next;

while (p) {

cout << p->data;

p = p->next;

if (p)

cout << ' ';

}

cout << endl;

}

int main() {

DLinkNode* L;

Initalize(L);

Push_Back(L, 1);

Push_Back(L, 2);

Push_Back(L, 3);

Push_Back(L, 4);

Push_Head(L, 5);

Push_Head(L, 6);

Push_Head(L, 7);

Push_Head(L, 8);

Print(L);

Delete(L, 3);

Print(L);

Pop_Head(L);

Print(L);

return 0;

}