C++链表操作

#define _CRT_SECURE_NO_DEPRECATE
#include<iostream>
//#include<malloc.h>
#include<stdio.h>
using namespace std;
struct Node
{
    int number;
    char *a;
    /*int grade;*/
    Node * next;
};
Node* insert(Node * &head/*, int num*/);
void del(Node * &head, int key);
void show(const Node * head);
void GreatList(Node * &head);
void main()
{
    int k;
    Node * head = NULL;
    cout << "初始化链表：" << endl;
    GreatList(head);
    cout << "插入学生：" << endl;
    insert(head/*, k*/);
    cout << "输入删掉的学生信息";
    cin >> k;
    del(head, k);
    show(head);
}
void GreatList(Node * &head)
{
    Node *s, *p = NULL;
    s = new Node;
    cin >> s->number;
    scanf("%s",&s->a);
    while (s->number != 0)
    {
        if (head == NULL)
            head = s;
        else
            p->next = s;//38行
        p = s;
        s = new Node;
        cin >> s->number;
        scanf("%s", &s->a);
    }
    p->next = NULL;
    delete s;
    return;
}
Node* insert(Node * &head/*, int num*/)
{
    Node * s, *p, *q,*sn,*pre;
    sn = head;//这里需要一个指针指向头结点
    pre = head;
    s = new Node;
    cin >> s->number;
    scanf("%s", &s->a);
    /*s->number = num;*/
    s->next = NULL;
    if (head == NULL)
    {
        head = s;
    }
    else 
    {
        while (s->number > sn->number&&sn->next!=NULL)
        {
            pre = sn;
            sn = sn->next;
        }
        if (s->number <= sn->number)
        {
            if (head == sn)
            {
                head = s;
                s->next = sn;
            }
            else
            {
                pre->next = s;
                s->next = sn;
            }
        }
        else
        {
            sn->next = s;
        }
    }
    return head;
}
void del(Node * &head, int key)
{
    Node * p;
    if (!head)
    {
        cout << "列表为空!\n";
        return;
    }
    if (head->number == key)
    {
        p = head;
        head = head->next;
        delete p;
        p = NULL;
        cout << key << "列表头节点已被删除\n";
        return;
    }

    for (Node * pg = head; pg->next!=NULL; pg = pg->next)
    {
        if (pg->next->number == key)
        {
            p = pg->next;
            pg->next = p->next;
            delete p;
            cout << key << "已被删除\n";
            return;
        }
    }
    cout << key << "不存在链表中\n";
}
void show(const Node * head)
{
    cout << "现在的列表为：";
    while (head)
    {
        cout << head->number << endl;
        char *arr = head->a;
        cout << arr;
        head = head->next;
    }
}