数据结构与算法-----双向线性链表

链表
1.基本特征：由一系列内存中不连续的节点组成，每个节点除了保存数据以外，还需要保存其前后节点的地址——双向链表。
2.基本操作
1)追加
2)插入
3)删除
4)遍历
5)伪随机访问
示例：使用C++实现双向链表类，并演示结果；

#include <iostream>
using namespace std;
class List {
public:
    // 构造函数中初始化为空链表
    List (void) : m_head (NULL), m_tail (NULL) {}
    // 析构函数中销毁剩余的节点
    ~List (void) {
        for (Node* next; m_head; m_head = next) {
            next = m_head -> m_next;
            delete m_head;
        }
    }
    // 追加
    void append (int data) {
        /* Node* node = new Node; node -> m_data = data; node -> m_prev = m_tail; node -> m_next = NULL; m_tail = node; */
        m_tail = new Node (data, m_tail);
        if (m_tail -> m_prev)
            m_tail -> m_prev -> m_next = m_tail;
        else
            m_head = m_tail;
    }
    // 插入
    void insert (size_t index, int data) {
        for (Node* find = m_head; find;
            find = find -> m_next)
            if (index-- == 0) {
                Node* node = new Node (data,
                    find -> m_prev, find);
                if (node -> m_prev)
                    node -> m_prev -> m_next = node;
                else
                    m_head = node;
                node -> m_next -> m_prev = node;
                return;
            }
        throw OverBound ();
    }
    // 删除
    void erase (size_t index) {
        for (Node* find = m_head; find;
            find = find -> m_next)
            if (index-- == 0) {
                if (find -> m_prev)
                    find -> m_prev -> m_next =
                        find -> m_next;
                else
                    m_head = find -> m_next;
                if (find -> m_next)
                    find -> m_next -> m_prev =
                        find -> m_prev;
                else
                    m_tail = find -> m_prev;
                delete find;
                return;
            }
        throw OverBound ();
    }
    // 正遍历
    void forward (void) const {
        for (Node* node = m_head; node;
            node = node -> m_next)
            cout << node -> m_data << ' ';
        cout << endl;
    }
    // 反遍历
    void backward (void) const {
        for (Node* node = m_tail; node;
            node = node -> m_prev)
            cout << node -> m_data << ' ';
        cout << endl;
    }
    // 下标运算符
    int& operator[] (size_t index) {
        for (Node* find = m_head; find;
            find = find -> m_next)
            if (index-- == 0)
                return find -> m_data;
        throw OverBound ();
    }
    const int& operator[] (size_t index) const {
        return const_cast<List&> (*this) [index];
    }
    // 测长
    size_t length (void) const {
        size_t len = 0;
        for (Node* node = m_head; node;
            node = node -> m_next)
            len++;
        return len;
    }
private:
    // 越界异常
    class OverBound : public exception {
    public:
        const char* what (void) const throw () {
            return "链表越界！";
        }
    };
    // 节点
    class Node {
    public:
        Node (int data = 0, Node* prev = NULL,
            Node* next = NULL) :
            m_data (data), m_prev (prev),
            m_next (next) {}
        int   m_data; // 数据
        Node* m_prev; // 前指针
        Node* m_next; // 后指针
    };
    Node* m_head; // 头指针
    Node* m_tail; // 尾指针
};
int main (void) {
    try {
        List list;
        list.append (10);
        list.append (20);
        list.append (50);
        list.append (60);
        list.append (80);
        list.forward ();
        list.insert (1, 15);
        list.insert (3, 40);
        list.insert (6, 70);
        list.backward ();
        list.erase (1);
        list.erase (2);
        list.erase (4);
        list.forward ();
        size_t len = list.length ();
        for (size_t i = 0; i < len; i++)
            list[i]++;
        const List& cr = list;
        for (size_t i = 0; i < len; i++)
            cout << cr[i] << ' ';
        cout << endl;
// cout << cr[10] << endl;
    }
    catch (exception& ex) {
        cout << ex.what () << endl;
        return -1;
    }
    return 0;
}

输出结果：