链表的面试题

1、比较顺序表和链表的优缺点，它们分别在什么场景下使用？
1）顺序表支持随机访问，单链表不支持随机访问。
2）顺序表插入/删除数据效率很低，时间复杂度为O(N)（除尾插和尾删），单链表插入/删除效率更高，时间复杂度为O(1)。
3）顺序表的CPU高速缓冲效率更高，单链表CPU高速缓冲效率低。

2、打印单向链表

void Display(pList plist)
{
    pNode cur = plist;
while (cur)
    {
printf("%d-->", cur->data);
         cur = cur->next;
    }
printf("over\n");
}

3、单链表的排序

void BubbleSort(pList *pplist)
{
    pNode cur = NULL;
    pNode tail = NULL;
    assert(pplist);
if ((*pplist == NULL) || (*pplist)->next == NULL)
    {
return;
    }
    cur = *pplist;
while (cur != tail)
    {
while (cur->next != tail)
        {
if (cur->data > cur->next->data)
            {
                DataType tmp = cur->data;
                cur->data = cur->next->data;
                cur->next->data = tmp;
            }
            cur = cur->next;
        }
        tail = cur;
        cur = *pplist;
    }
}

4、逆序打印单项链表

void ReversePrint(pList plist)
{
    pNode cur = plist;
if (cur == NULL)
    {
return;
    }
if (cur->next != NULL)
    {
        ReversePrint(cur->next);
    }
    printf("%3d", cur->data);
}

5、删除无头单链表的非尾结点

void EraseNotTail(pNode pos)
{
    pNode del = NULL;
    assert(pos);
    assert(pos->next != NULL);
pos->data = pos->next->data;
    del = pos->next;
pos->next = pos->next->next;
    free(del);
    del = NULL;
}

6、在无头单链表的非头结点前插入一个元素

void InsertFrontNode(pNode pos, DataType x)
{
    pNode newnode = NULL;
    DataType tmp;
    assert(pos);
    newnode = BuyNode(x);
    newnode->next = pos->next;
    pos->next = newnode;
    tmp = pos->data;
    pos->data = pos->next->data;
    pos->next->data = tmp;
}

7、约瑟夫环问题

void JosephCycle(pList *pplist, int k)
{
    pNode cur = NULL;
    pNode del = NULL;
    assert(pplist);
    cur = *pplist;
while (cur->next != cur)//留一个数
    {
        int i = 0;
        for (i = 0; i < k - 1; i++)
        {
            cur = cur->next;
        }
        del = cur->next;
        printf("%d", cur->data);
        cur->data = cur->next->data;
        cur->next = cur->next->next;
        free(del);
        del = NULL;
    }
    printf("%d\n", cur->data);
}

8、逆序单向链表

void ReverseList(pList *pplist)
{
    DataType tmp = NULL;
    pNode Next = NULL;
    pNode cur = NULL;
    assert(pplist);
if ((*pplist == NULL) || (*pplist)->next == NULL)
    {
        return;
    }
    cur = *pplist;
Next = cur->next;
    cur->next = NULL;
while (Next != NULL)
    {
        tmp = Next->next;
Next->next = cur;
        cur = Next;
Next = tmp;
    }
    *pplist = cur;
}

9、合并两个有序列表

pList Merge(const pList *p1, const pList *p2)
{
    pList newlist = NULL;
    pList list1 = NULL;
    pList list2 = NULL;
    pList tail = NULL;
    assert(p1 && p2);
    list1 = *p1;
    list2 = *p2;
if (list1 == list2)//同为一条链表，或都为空链表
    {
return NULL;
    }
if (list1 == NULL)
    {
return list2;
    }
if (list2 == NULL)
    {
return list1;
    }
if (list1->data < list2->data)//新链表的首部
    {
        newlist = list1;
        list1 = list1->next;
    }
else
    {
        newlist = list1;
        list1 = list1->next;
    }
    tail = newlist;
while (list1 && list2)
    {
if (list1->data && list2->data)
        {
            tail->next = list1;
            list1 = list1->next;
            tail = tail->next;
        }
else
        {
            tail->next = list2;
            list2 = list2->next;
            tail = tail->next;
        }
    }
if (list1 = NULL)
    {
        tail->next = list2;
    }
else
    {
        tail->next = list1;
    }
return newlist;
}

10、查找单链表的中间节点，要求只能遍历一次链表
//定义两个指针分别为fast和slow，fast每次跳两下，slow每次跳一下，
//当fast指向链尾时，show所指的位置就是中间结点

pNode FindMidNode(pList plist)
{
    pNode fast = plist;
    pNode slow = plist;
while (fast && (fast->next))
    {
        fast = fast->next->next;
        slow = slow->next;
    }
return slow;
}

11、查找单链表的倒数第k个节点，要求只能遍历一次链表
//定义两个指针分别为fast和slow，让fast先走k-1步后slow再走，当fast指向尾部时，slow所指向的就是倒数第k个元素

pNode FindKNode(pList plist, int k)
{
    pNode fast = plist;
    pNode slow = plist;
while (fast && fast->next)
    {
if (--k <= 0)//k次后，slow再走
        {
            slow = slow->next;
        }
        fast = fast->next;
    }
if (k <= 0)//执行完while后才能输出
    {
return slow;
    }
return NULL;
}

12、判断链表带环情况
//定义两个指针分别为fast和slow，每次fast比slow多走一步，如果带环，那么它们一定相交

pNode CheckCircle(pList plist)
{
    pNode fast = plist;
    pNode slow = plist;
while (fast && fast->next)
    {
        fast = fast->next->next;
        slow = slow->next;
if (fast == slow)//带环
        {
return fast;
        }
    }
return NULL;
}

13、求环的长度

int GetCircleLength(pNode meet)
{
    pNode pnode = meet->next;//meet为相遇点
int i = 1;
while (pnode != meet)
    {
        pnode = pnode->next;
        i++;
    }
return i;
}

14、求环的入口点

pNode GetCycleEntryNode(pList plist, pNode meet)
{
    pNode pnode = plist;
if ((plist == NULL) && (meet == NULL))
    {
return NULL;
    }
while(pnode != meet)
    {
        meet = meet->next;
        pnode = pnode->next;
    }
return meet;
}

15、判断两条单项链表是否相交

int CheckCross(pList list1, pList list2)
{
    pNode p1 = list1;
    pNode p2 = list2;
while (p1 && p1->next)
    {
        p1 = p1->next;
    }
while (p2 && p2->next)
    {
        p2 = p2->next;
    }
if ((p1 == p2) && (p1 != NULL))//相交
    {
return 1;
    }
else
return -1;
}

16、转化成不带环的链表求解

pNode GetCrossNoCycle(pList list1, pList list2)
{
    pNode meet = NULL;
    pNode cur = list1;
    pNode crossNode = NULL;
while (cur && cur->next)
    {
        cur = cur->next;
    }
    cur->next = list2;
    meet = CheckCircle(list1);
    crossNode = GetCycleEnterNode(list1, meet);
return crossNode;
}

17、求交点

pNode GetCrossNode(pList list1, pList list2)
{
    pNode p1 = CheckCircle(list1);//1表带环；0表不带环
    pNode p2 = CheckCircle(list2);
    pNode crossNode = NULL;
if (p1 == NULL && p2 == NULL)//不带环
    {
        crossNode = GetCrossNoCycle(list1, list2);
return crossNode;
    }
else if (p1 && p2)
    {
        pNode endNode = NULL;
        pNode cur = NULL;
//找到环入口的第一个结点
        endNode = GetCycleFrontEntryNode(list1, p1);
        cur = endNode->next;//保存环的入口
        endNode->next = NULL;//将环断开成两个不带环的链表
        crossNode = GetCrossNoCycle(list1, list2);
        endNode->next = cur;
    }
return crossNode;
}

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链表的面试题

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