具有一个元素的双向循环链表的反转

Question

我怀疑如果我们有一个只有一个节点（即）头的双向循环链表，并且如果我写 head.next = NULL，那么 head.prev 也会指向 NULL?

Answer 1

如果 head.next = NULL，则如下所示：

head.prev 仍然指向 head，如您的 post 所示。

Answer 2

如果 head.next = NULL，它不会改变 head.prev（它仍然指向 HEAD

您可以运行下面的一段代码来检查它是如何工作的。（C++ 实现）

struct Node 
{ 
    int data; 
    struct Node *next; 
    struct Node *prev; 
};
void insertEnd(struct Node** start, int value) 
{ 
    if (*start == NULL) 
    { 
        struct Node* new_node = new Node; 
        new_node->data = value; 
        new_node->next = new_node->prev = new_node; 
        *start = new_node; 
        return; 
    } 
  
    Node *last = (*start)->prev; 
  
    struct Node* new_node = new Node; 
    new_node->data = value; 
  
    new_node->next = *start; 
  
    (*start)->prev = new_node; 
  
    new_node->prev = last; 
  
    last->next = new_node; 
} 
int32_t main(){
    FastIO;
    struct Node* start = NULL; 
    insertEnd(&start, 5); 
    cout << start -> next->data << endl;
    cout << start -> prev->data << endl;
    start -> next = NULL;
    if(start->next) cout << "Next is Null\n";
    else cout << "Next is not Null\n";
    if(start->prev) cout << "Prev is Null\n";
    else cout << "Prev is not Null\n";
    return 0;
}

具有一个元素的双向循环链表的反转

Reverse of a doubly circular linked list having one element

linked-list

circular-dependency

data-structures