Data Structure - linked list ADT (C/C++ language)

#include<stdlib.h>
#include<stdio.h>

#define OK 1
#define ERROR 0
#define OVERFLOW -1
#define TRUE 1
#define FALSE 0

typedef int ElemType;//Specify the data type in the linked list
typedef int Status;

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


Status GetElem_L(LinkList L, int i, ElemType &e)
{
	//L is the head pointer of the singly linked list with the head node
	//When the i-th element exists, assign its value to e and return OK, otherwise return ERROR
	LinkList p;int j;
	p = L->next; j = 1; //Initialization, p points to the first node, j is the counter
	while (p&&j < i) //Search backwards until p points to the i-th element or p is empty
	{
		p = p->next; ++j;
	}
	if (!p || j>i)return ERROR; //The i-th element does not exist
	e = p->data; //take the i-th element
	return OK;
}

Status ListInsert_L(LinkList &L, int i, ElemType e)
{
	//Insert element e before the i-th position in the singly linked list L with the head node
	LinkList p, s; int j;
	p = L;j = 0;
	while (p&&j < i - 1) //find the i-1th node
	{
		p = p->next;
		++j;
	}
	if (!p || j>i - 1)return ERROR; //i is less than 1 or greater than table length+1
	s = (LinkList)malloc(sizeof(LNode)); //Generate a new node
	s->data = e; s->next = p->next; //insert into LL
	p->next = s;
	return OK;
}

Status ListDelete_L(LinkList &L, int i, ElemType &e)
{
	//In the singly linked list L with the head node, delete the i-th element and return its value by e
	LinkList p, q; int j;
	p = L; j = 0;
	while (p->next&&j < i - 1) //find the i-th node and make p point to its predecessor
	{
		p = p->next;
		++j;
	}
	if (!(p->next) || j>i - 1)return ERROR; //The delete position is unreasonable
	q = p->next; p->next = q->next; // delete and release the node
	e = q->data; free(q);
	return OK;
}

void CreateList_L(LinkList &L, int n)
{
	//Enter the values ​​of n elements in reverse order, and create a singly linked list L with the head node
	L = (LinkList)malloc(sizeof(LNode));
	L->next = NULL; //Create a singly linked list with a head node first
	int i; LinkList p;
	for ( i = n; i > 0; --i)
	{
		p = (LinkList)malloc(sizeof(LNode)); //Generate a new node
		scanf("%d", &p->data); //input element value
		p->next = L->next;
		L->next = p; //Insert into header
	}
}

void Display(LinkList &L)
{
	LinkList p;
	p = L->next;
	while (p) //find the i-th node and let p point to its predecessor
	{
		printf("%d ", p->data);
		p = p->next;
	}
	printf("\n");
}
intmain()
{
	LinkList L;
	ElemType e;
	CreateList_L(L, 5);
	Display(L);
	ListDelete_L(L, 2, e);
	printf("%d", e);
	Display(L);
	ListInsert_L(L, 2, e);
	printf("%d", e);
	Display(L);
	return 0;
}