Definition and representation of singly linked list

• Singly linked list storage structure

typedef struct Lnode{
ElemType    data;
struct    Lnode   *next;
}Lnode,*LinkList

• Initialization of the singly linked list
  (1) Generate a new node as the head node, use the head pointer L to point to the head node
  (2) empty the pointer field of the head node.

Algorithm Description

Status InitList_L(LinkList &L){
  	L=new LNode;
  	L->next=NULL;
  	return OK;
}

• Determine whether the linked list is empty:
  an empty list means that there is no element in the linked list, but the head pointer and head node still exist.
  Idea: determine whether the head node pointer field is empty

int ListEmpty(LinkList L){
	if(L->next)
		return 0;
	else
		return 1;
}

Returns 1 if L is an empty list, otherwise returns 0.

• Singly linked list destruction
  idea: starting from the head pointer, release all nodes in turn

Status DestroyList_L(LinkList &L){
	Lnode *p;
	while(L){
		p=L;
		L=L->next;
		delete p;
	}
}

• Clear the linked list
  The linked list still exists, but there are no elements in the linked list Idea
  : release all nodes in turn, and set the head node pointer field to empty

Status ClearList(LinkList &L){
	Lnode *p,*q;
	p=L->next;
	while(p){
		q=p->next;
		delete p;
		p=q;
	}
	L->next=NULL;
	return OK;
}

• Find the length of the singly linked list L

int ListLength_L(LinkList L){
	LinkList p;
	p=L-next;
	i=0;
	while(p){
		i++;
		p=p->next;
	}
}

• Value-take the content of the i-th element in the singly linked list
  Linked list is not a random access structure, so it needs to search down one by one node.
  Algorithm steps:

1. Scan along the chain from the first node (L->next), use the pointer p to point to the currently scanned node, and the initial value of p=L->next.
2. j is used as a counter to accumulate the number of nodes currently scanned, and the initial value of j is 1
3. When p points to the next node scanned, the counter j is incremented by 1.

Status GetElem_L(LinkList L, int i, ElemType &e){
	p=L->next;   j=1;
	while(p&&j<i){
		p=o->next;++j;
	}
	if(!p||j>i)
		return ERROR;
	e=p->data;
	return OK;
}

• Insert node
  Insert a new node with value e before the i-th node
  Algorithm diagram:
  
  code:

Status ListInsert_L(LinkList &L,int i, ElemType e){
	p=L;j=0;
	while(p&&j<i-1){
		p=p->next;++j;
	}
	if(!p||j>i-1)
		return ERROR;
	s=new LNode;
	s->data=e;
	s->next=p->next;
	p->next=s;
	return OK;
}

• delete node