Creation of circular linked list and controllable output

The creation and basic operation of circular linked list

In the last part, we talked about the use of The first interpolation and The tail interpolation How to create a single linked list , Two methods of comparison . Then we learn the creation of circular linked list .

As long as you learn how to create a single linked list , The creation of circular linked list becomes very simple .

Circular linked list creation
The structure of single linked list ：

Circular linked list ：

The so-called circular linked list , That is, the tail node of the single linked list end A pointer to the domain That is to say end->next Point to the address of the head node ： end->next = head . This completes the creation of circular linked list .
It's over ？ Of course, it's not that simple ~~~

Circular linked list is different from single linked list , The reason is that when we talked about single linked list last time , The tail node pointer field always points to NULL, That is to say end->next = NULL. Therefore, the sign for judging the end of the single linked list , Namely while( node->next != NULL) , But the tail node of the circular linked list does not point to NULL , It is Head node head. therefore , Our judgment criteria should also be changed .

After thinking , Decide to assign the data field of the head node to -1, So there's a sign , Used to judge whether the circular linked list is executed once .

thought without learning is perilous , Get started now ！

Linklist Creat_list(Linklist head) {
	LNode *node = NULL;
	LNode *end = NULL;
	head = (Linklist)malloc(sizeof(LNode));
	head->next = NULL;
	head->data = -1;
	end = head;
	int count = 0;
	printf("Input node numbers: ");
	scanf("%d", &count);
	for (int i = 0; i < count; i++) {
		node = (LNode*)malloc(sizeof(LNode));
		node->data = i;
		end->next = node;
		end = node;
	}
	end->next = head;            //   Point the pointer of the tail node to the head node 
	return head;
}

This completes the creation of circular linked list , Next, we need to find a way to make the circular linked list execute the number of cycles as we expected .
focused , I came up with this function to judge the number of nodes in a circular linked list .

int node_number(Linklist *head) {
	Linklist tem = head;
	tem = tem->next;              //   The header of the node is the value of the field -1, Therefore, we need to start from the next node of the node 
	int count = 0;                //   Count the number of nodes  
	while (tem->data != -1){               //   Because the data field of the head node is assigned -1, therefore -1 Equivalent to a label 
		count++;                        //   Not once , One more knot point 
		tem = tem->next;           //   Next node 
	}
	return count + 1;              //   Because before the first execution of the loop , Skipped the header node , So I got count  No head node , When we return, we add 1
}

In this way, we get the number of nodes of the circular linked list .
As long as you have the number of nodes , We can output the number of all nodes of the circular linked list according to our requirements .

void Illustrate(Linklist head) {
	Linklist tem = head;
	int size = node_number(head)*2;           //  *2  Indicates that the circular linked list will be executed twice 
	for (int i = 0; i < size; i++) {          //  size  Indicates the number of nodes to pass .
		printf("%d   ", tem->data);
		tem = tem->next;
	}
}

In this way, we have completed the creation of circular linked list and control output .