常见链表面试题

头文件以及定义的节点都在上一篇的单链表功能实现里面有写

逆序打印单链表

递归方式简洁明了

void linklist_reverseprintf(linklist *head)
{
    if(head == NULL)
    {
        return;//空链表
    }
    linklist_reverseprint(head->next);
    printf("[%c|%p]\n",head->data,head);
}

不允许遍历链表，在pos之前插入

void swap(linktype *a,linktype *b)
{
    linktype t = *a;
    *a = *b;
    *b = t;
}
void linklist_insertbefore(linklist **head,linklist *pos,linktype value)
{
    if(head == NULL)
    {
        return;//非法输入
    }
    if(*head == NULL)
    {
        return;//空
    }
    if(*head->next == NULL)
    {
        linklist_pushhead(head,value);
        //如果只有一个元素就调用头插函数
    }
    else
    {
        linklist *newnode=creat(value);
        newnode->next=pos->next;
        pos->next=newnode;
        swap(&pos->data,&newnode->data);
    }
}

单链表的逆置

void linklist_nizhi(linklist **head)
{
    if(head == NULL)
    {
        return;
    }
    if(*head == NULL)
    {
        return;//空链表
    }
    if(*head->next == NULL)
    {
        return *head;
    }
    else
    {
        linklist *cur = *head;
        while(cur->next != NULL)
        {
            linktype value = cur->next->data;
            linklist_pop1(head,cur->next);
            linklist_pushfront(*head,value)
        }
        return *head;
    }
}

单链表的冒泡排序

void linklist_bubble(linklist **head)
{
    if(head == NULL)
    {
        return;//非法输入
    }
    if(*head == NULL)
    {
        return;//空
    }
    else
    {
        linklist *cur = *head;
        linklist *tail = NULL;
        linklist *pos = *head;
        for(;cur->next != NULL;cur=cur->next)
        {
            for(;pos->next!=tail;pos=pos->next)
            {
                if(pos->data>pos->next->data)
                {
                    swap(&pos->data,&pos->next->data)
                }

            }
            tail = pos;
        }
    }
}

将两个链表合并为一个有序链表

linklist *linklist_merge(linklist *head1,linklist *head2)
{
    if(head1 == NULL)
    {
        return head2;
    }
    if(head2 == NULL)
    {
        return head1;
    }
    else
    {
        linklist *cur1 = head1;
        linklist *cur2 = head2;
        linklist *newhead = NULL;
        linklist *newtail = NULL;
        if(cur1->data<cur2->data)
        {
            newhead = newtail = cur1
            cur1 = cur1->next;

        }
        else
        {
            newhead = newtail = cur2;
            cur2 = cur2->next;
        }
        while(cur1 != NULL &&cur2 != NULL)
        {
            if(cur1->data <= cur2->data)
            {
                newtail->next = cur1;
                newtail = newtail->next;
                cur1 = cur1->next;
            }
            else
            {
                newtail->next = cur2;
                newtail = newtail->next;
                cur2 = cur2->next;
            }
        }
        if(cur1 == NULL)
        {
            newtail->next = cur2;
        }
        else
        {
            newtail->next = cur1;
        }
        return newhead;
    }
}

找到倒数第k个节点

linklist_size(linklist *head)
{
    if(head == NULL)
    {
        return;//空
    }
    else
    {
        size_t count = 0;
        linklist *cur = head;
        while(cur != NULL)
        {
            cur = cur->next;
            count++;
        }
        return count;
    }
}
linklist *linklist_findlastknode(linklist *head,size_t k)
{
    if(head == NULL)
    {
        return NULL;//空
    }
    if(k > linklist_size(head))
    {
        return NULL;//超过了范围
    }
    else
    {
        size_t i=linklist_size(head)-k;
        linklist *cur = head;
        for(;i>0;i--)
        {
            cur = cur->next;
        }
        return cur;
    }
}

删除倒数第k个节点

void linklist_eraselastknode(linklist **head,size_t k)
{
    if(*head == NULL)
    {
        return;//非法输入
    }
    if(head == NULL)
    {
        return;//空
    }
    if(k > linklist_size(head))
    {
        return;//超范围
    }
    else
    {
        linklist *pos = linklist_findlastknode(head,k);
        linklist_erase(head,pos);
    }
}

判断链表是否带环，如果带环则返回入口点

linklist *linklist_getenter(linklist *head)
{
    if(head == NULL)
    {
        return;
    }
    else
    {
        linklist *fast = head;
        linklist *slow = head;
        while(fast &&fast->next)
        {
            fast = fast->next->next;
            slow = slow->next;
            if(fast == slow)
            {
                linklist *meet = fast;
                linklist *cur = head;
                while(meet != cur)
                {
                    cur = cur->next;
                    meet = meet->next;
                }
                return meet;

            }
        }
        return NULL;
    }

}

判断两个链表是否相交，如果相交就返回交点（不带环）

“`
linklist *linklist_iscross(linklist *head1,linklist *head2)
{
if(head1 == NULL)
{
return NULL;
}
if(head2 == NULL)
{
return NULL;
}
else
{
linklist *cur1 = head1;
linklist *cur2 = head2;
while(cur1 != NULL)
{
cur1 = cur1->next;
}
while(cur2 != NULL)
{
cur2 = cur2->next;
}
if(cur1 == cur2)
{
size_t len = 0;
len1 = linklist_size(head1);
len2 = linklist_size(head2);
linklist *pos1 = head1;
linklist *pos2 = head2;
if(len1-len2)
{
size_t len = len1-len2;
for(;len>0;len–)
{
pos1 = pos1->next;
}
}
else
{
size_t len = len2-len1;
for(;len>0;len–)
{
pos2 = pos2->next;
}
}
while (pos1 != pos2)
{
pos1 = pos1->next;
pos2 = pos2->next;
}
return pos1;
}
return NULL;
}
}