单链表的实现

// SListTest.h
#ifndef _SLIST_TEST_H_
#define _SLIST_TEST_H_

struct SNode
{
    int data;
    SNode *next;
};

class SListTest
{
public:
        SListTest(void);
        ~SListTest(void);

        bool isEmpty(void);
        int length(void);
        SNode * find(int pos);

        /* insert before pos */
        bool insert(int pos, int newItem);
        bool remove(int pos);

private:
        int len;
        SNode *head;
};

#endif // _SLIST_TEST_H_

// SListTest.cpp
#include <stdio.h>
#include "SListTest.h"

SListTest::SListTest(void)
{
    len = 0;
    head = new SNode();
}

SListTest::~SListTest(void)
{
    while(!isEmpty())
    {
        remove(0);
    }
}

bool SListTest::isEmpty(void)
{
    bool ret = false;

    if(len <= 0)
    {
        ret = true;
    }

    return ret;
}

int SListTest::length(void)
{
    return len;
}

SNode * SListTest::find(int pos)
{
    SNode *ret = NULL;
    SNode *now = NULL;

    if(pos < 1 || pos > length())
    {
        return ret;
    }

    now = head;
    while(pos > 0)
    {
        now = now->next;
        --pos;
    }
    ret = now;

    return ret;
}

/* insert before pos */
bool SListTest::insert(int pos, int newItem)
{
    bool ret = false;

    if(pos < 1 || pos > length() + 1)
    {
        return ret;
    }

    SNode * node = new SNode();
    node->data = newItem;

    if(pos == 1)
    {
        node->next = head->next;
        head->next= node;
    }
    else
    {
        SNode *now = find(pos - 1);
        if(now)
        {
            node->next = now->next;
            now->next = node;
        }
    }

    ++len;
    ret = true;

    return ret;
}

bool SListTest::remove(int pos)
{
    bool ret = false;

    if(pos < 1 || pos > length())
    {
        return ret;
    }

    SNode *now = find(pos);
    if(now)
    {
        SNode *prev = find(pos - 1);
        prev->next = now->next;
        delete now;
    }

    --len;
    ret = true;

    return ret;
}

#include <stdio.h>
#include "SListTest.h"

int main()
{
    SListTest *list = new SListTest();

    /* insert before pos */
    list->insert(1, 123); // head -> 123
    list->insert(1, 456); // head -> 456 -> 123
    list->insert(2, 789); // head -> 456 -> 789 -> 123

    list->remove(3); // head -> 456 -> 789

    return 0;
}