错误记录，链表建立逻辑错误

#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;

typedef struct LNode
{
	int data;
	struct LNode* next;
}LNode;

int main()
{
	void createlist(LNode*&, int);
	void mergelist(LNode*, LNode*, LNode*&);
	void printlist(LNode*);
	LNode* a, * b, * c;
	int n1, n2;

	cout << "Please enter the length of the first linked list:";
	cin >> n1;
	createlist(a, n1);
	cout << "Please enter the length of the second linked list:";
	cin >> n2;
	createlist(b, n2);
	mergelist(a, b, c);
	printlist(c);
	
	return 0;
}

void createlist(LNode*& a, int n)
{
	LNode* p;

	a = (LNode*)malloc(sizeof(LNode));
	p = a->next;
	cout << "Please enter the elements of the linked list one by one in an increasing order:";
	for (int i = 0; i < n; i++)
	{
		cin >> p->data;
		p->next = (LNode*)malloc(sizeof(LNode));
		p = p->next;
	}
	p->next = NULL;

	return;
}

void mergelist(LNode* a, LNode* b, LNode*& c)
{
	LNode* p;

	c = (LNode*)malloc(sizeof(LNode));
	p = c->next;
	while (a != NULL && b != NULL)
	{
		if (a->data < b->data || b == NULL)
		{
			p->data = a->data;
			a = a->next;
		}
		else
		{
			p->data = b->data;
			b = b->next;
		}
		p->next = (LNode*)malloc(sizeof(LNode));
		p = p->next;
	}
	p->next = NULL;

	return;
}

void printlist(LNode* a)
{
	a = a->next;
	while (a)
	{
		cout << a->data;
		if (a->next)
		{
			cout << " - ";
		}
	}

	return;
}