数据结构---单链表（常见的复杂操作）

news2024/9/20 5:39:42

一、单链表

1.1.查找中间元素

1.2.查找倒数第K个节点

1.3.链表倒置

1.4.冒泡排序

1.5.选择排序

1.6.环，确认有环单链表的环入口和环大小

二、总结

一、单链表

1.1.查找中间元素

定义两个指针，分别指向第一个元素，第一个指针每次向后遍历两个节点，第二个指针向后遍历一个节点，最终当第一个指针遍历到最后一个时，第二个也就刚好指向中间节点。

LinkList *FindMidLinkList(LinkList *phead)
{
    LinkList *pfast = NULL;
    LinkList *pslow = NULL;
    if (phead->pnext == NULL)
    {
        return NULL;
    }

    pfast = pslow = phead->pnext;
    while (pfast != NULL)
    {
        pfast = pfast->pnext;
        if (NULL == pfast)
        {
            break;
        }
        pfast = pfast->pnext;
        if (NULL == pslow)
        {
            break;
        }

        pslow = pslow->pnext;
    }

    return pslow;

}

1.2.查找倒数第K个节点

定义两个指针，分别指向头节点，先让第一个指针向后遍历k次，让两个指针之间相差k个位置，然后让他们一起向后遍历，直到第一个指针指向最后一个节点，此时第二个指针就指向倒数第k个位置。

LinkList *FindTailKLinkList(LinkList *phead, int k)
{   
    LinkList *pfast = NULL;
    LinkList *pslow = NULL;

    if (phead->pnext == NULL)
    {
        return NULL;
    }

    pfast = phead;
    pslow = phead;

    for (int i = 0; i < k; i++)
    {
        pfast = pfast->pnext;
        if (pfast == NULL)
        {
            break;
        }
    }

    if (pfast == NULL)
    {
        return phead;
    }

    while (pfast != NULL)
    {
        pfast = pfast->pnext;
        pslow = pslow->pnext;
    }

    return pslow;

}

1.3.链表倒置

将链表的数据链与头节点分开，然后依次头插法插入头节点后面，完成倒置

int HeadInvertLinkList(LinkList *phead)
{
    LinkList *ptmp = NULL;
    LinkList *qtmp = NULL;

    ptmp = phead->pnext;
    phead->pnext = NULL;
    qtmp = ptmp;

    while(qtmp != NULL)
    {
        qtmp = qtmp->pnext;
        ptmp->pnext = phead->pnext;
        phead->pnext = ptmp;
        ptmp = qtmp;
    }


    return 0;
}

1.4.冒泡排序

int BulleSortLinkList(LinkList *phead)
{
    LinkList *ptmp1 = NULL;
    LinkList *ptmp2 = NULL;
    LinkList *qtmp = NULL;

    DataType data = 0;

    //链表只有头节点或只有一个数据节点,不需要排序
    if (phead->pnext == NULL || phead->pnext->pnext == NULL)
    {
        return 0;
    }

    ptmp1 = phead->pnext;
    ptmp2 = phead->pnext->pnext;

    

    while (1)
    {
        ptmp1 = phead->pnext;
        ptmp2 = phead->pnext->pnext;


        if (ptmp2 == qtmp)
        {
            break;
        }

        while (ptmp2 != qtmp)
        {
            if (ptmp1->data < ptmp2->data)
            {
                data = ptmp1->data;
                ptmp1->data = ptmp2->data;
                ptmp2->data = data;
            }
            ptmp1 = ptmp1->pnext;
            ptmp2 = ptmp2->pnext;
        }
        qtmp = ptmp1;


    }

    return 0;

}

1.5.选择排序

int SelectSortLinkList(LinkList *phead)
{
    LinkList *ptmp1 = NULL;
    LinkList *ptmp2 = NULL;
    LinkList *qtmp = NULL;
    DataType data = 0;

     //链表只有头节点或只有一个数据节点,不需要排序
    if (phead->pnext == NULL || phead->pnext->pnext == NULL)
    {
        return 0;
    }

    qtmp = phead->pnext;

    while (qtmp->pnext != NULL)
    {
        ptmp1 = qtmp;
        ptmp2 = qtmp->pnext;

        while(ptmp2 != NULL)
        {
            if (ptmp2->data < ptmp1->data)
            {
                ptmp1 = ptmp2;
            }
            ptmp2 = ptmp2->pnext;
        }

        if (ptmp1 != qtmp)
        {
            data = ptmp1->data;
            ptmp1->data = qtmp->data;
            qtmp->data = data;
        }

        qtmp = qtmp->pnext;
    }

}

1.6.环，确认有环单链表的环入口和环大小

定义两个指针，分别指向第一个元素，第一个指针每次向后遍历两个节点，第二个指针向后遍历一个节点，可以保证两个指针的差程自然数增长，这样两个指针终会在环里相遇。

LinkNode *IsHasCircle(LinkNode *pHead, int *pcnt)
{
    LinkNode *pFast = NULL;
    LinkNode *pSlow = NULL;
    LinkNode *pTmpNode = NULL;
    LinkNode *pNode1 = NULL;
    LinkNode *pNode2 = NULL;
    int ret = 0;
    int cnt = 1;

    pSlow = pFast = pHead->pNext;
    while (1)
    {
        pFast = pFast->pNext;
        if (NULL == pFast)
        {
            ret = 0;
            break;
        }
        pFast = pFast->pNext;
        if (NULL == pFast)
        {
            ret = 0;
            break;
        }

        pSlow = pSlow->pNext;
        if (pSlow == pFast)
        {
            ret = 1;
            break;
        }
    }

    if (1 == ret)
    {
        //获得环长
        pTmpNode = pSlow->pNext;
        while (pTmpNode != pSlow)
        {
            cnt++;
            pTmpNode = pTmpNode->pNext;
        }
        *pcnt = cnt;

        //获得环入口位置
        pNode1 = pSlow;
        pNode2 = pHead->pNext;
        while (1)
        {
            pNode1 = pNode1->pNext;
            pNode2 = pNode2->pNext;
            if (pNode1 == pNode2)
            {
                return pNode1;
            }
        }
    }

    return NULL;
}