静态链表

使用游标（cursor）来模拟指针，由程序员自己编写“分配结点”和“回收结点”的过程。

每个节点应含有两个域：element域和next域。

next域是游标指示器，指示其后继结点在结构数组中的相对位置（即数组的下标），数组的第0个分量可以设计成表的头结点。

//文件 CursorList.h，静态链表的定义
#ifndef CursorList_
#define CursorList_

template <class Object>
class CursorListItr;

template <class Object>
class CursorList
{
public:
    CursorList();
    CursorList(const CursorList & rhs);
    ~CursorList();

    bool isEmpty() const;
    void makeEmpty();
    CursorListItr<Object> first() const;
    void insert(const Object & x, const CursorListItr<Object> & p);
    CursorListItr<Object> find(const Object & x) const;
    CursorListItr<Object> findPrevious(const Object & x) const;
    void remove(const Object & x);
public:
    struct CursorNode
    {
        CursorNode() : next(0) {}
    private:
        CursorNode(const Object & theElement, int n):element(theElement), next(n) {}
        Object element;
        int next;
        friend class CursorList<Object>;
        friend class CursorListItr<Object>;
    };
private:
    int header;

    static vector<CursorNode> cursorSpace;

    static void initializeCursorSpace();
    static int alloc();
    static void free(int p);

    friend class CursorListItr<Object>;
};

//CursorListItr类：维护 "当前位置"
template <class Object>
class CursorListItr
{
public:
    CursorListItr() : current(0) {}
    bool isPastEnd() const
    { return current == 0; }
    void advance()
    {
        if (!isPastEnd())
            current = CursorList<Object>::cursorSpace[current].next;
    }
    const Object & retrieve() const
    {
        if (isPastEnd()) throw BadIterator();
        return CursorList<Object>::cursorSpace[current].element;
    }
private:
    int current;       //当前位置
    friend class CursorList<Object>;

    CursorListItr(int theNode) : current(theNode) { }
};
#endif // CursorList_

//静态链表的主要实现如下面代码所示
#include "CursorList.h"

//初始化
template <class Object>
void CursorList<Object>::initializeCursorSpace()
{
    static int cursorSpaceIsInitialized = false;

    if (!cursorSpaceIsInitialized)
    {
        cursorSpace.resize(100);
        for (int i = 0; i < cursorSpace.size(); i++)
            cursorSpace[i].next = i + 1;
        cursorSpace[cursorSpace.size() - 1].next = 0;
        cursorSpaceIsInitialized = true;
    }
}

//分配结点
template <class Object>
int CursorList<Object>::alloc()
{
    int p = cursorSpace[0].next;
    cursorSpace[0].next = cursorSpace[p].next;
    return p;
}

//释放结点
template <class Object>
void CursorList<Object>::free(int p)
{
    cursorSpace[p].next = cursorSpace[0].next;
    cursorSpace[0].next = p;
}

//构造静态表
template <class Object>
CursorList<Object>::CursorList()
{
    initializeCursorSpace();
    header = alloc();
    cursorSpace[header].next = 0;
}

//逻辑判空
template <class Object>
bool CursorList<Object>::isEmpty() const
{
    return cursorSpace[header].next == 0;
}

//在p所指向单元后插入x
template <class Object>
void CursorList<Object>::insert(const Object & x, const CursorListItr<Object> & p)
{
    if (p.current != 0)
    {
        int pos = p.current;
        int tmp = alloc();

        cursorSpace[tmp] = CursorNode(x, cursorSpace[pos].next);
        cursorSpace[pos].next = tmp;
    }
}

//返回值为x的第一个结点
template <class Object>
CursorListItr<Object> CursorList<Object>::find(const Object & x) const
{
    int itr = cursorSpace[header].next;
    while (itr != 0 && cursorSpace[itr].element != x)
        itr = cursorSpace[itr].next;
    return CursorListItr<Object>(itr);
}

//返回值为x的第一个结点的前驱
template <class Object>
CursorListItr<Object> CursorList<Object>::findPrevious(const Object & x) const
{
    int itr = header;
    while (cursorSpace[itr].next != 0&&cursorSpace[cursorSpace[itr].next].element != x)
        itr = cursorSpace[itr].next;
    return CursorListItr<Object>(itr);
}

//删除第一个值为 x的元素
template <class Object>
void CursorList<Object>::remove(const Object & x)
{
    CursorListItr<Object> p = findPrevious(x);  //查找前驱
    int pos = p.current;

    if (cursorSpace[pos].next != 0)
    {
        int tmp = cursorSpace[pos].next;
        cursorSpace[pos].next = cursorSpace[tmp].next;
        free (tmp);
    }
}