一个实现链表的基本操作程序，发生段错误

Question

问题遇到的现象和发生背景

问题相关代码，请勿粘贴截图

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct LNode {
    int date;
    struct LNode *next;
} Node;
#define len sizeof(Node)
Node *creat(int n);
void output(Node *begin);
void get(Node *begin, int n);
Node *insert(Node *begin, int n, int x);
Node *delet(Node *begin, int n);

int main() {
    int n, ret, x, i;
    char ch[4][20] = {{"show"}, {"delete"}, {"insert"}, {"get"}};
    char str[20];
    scanf("%d", &n);
    Node *begin;
    begin = creat(n);
    int count;
    scanf("%d", &count);

    while (count) {
        scanf("%s", str);

        for (i = 0; i < 4; i++)
            if (strcmp(ch[i], str) == 0)
                break;

        switch (i) {
            case 0:
                output(begin);
                break;

            case 1:
                scanf("%d", &n);
                begin = delet(begin, n);
                break;

            case 2:
                scanf("%d%d", &n, &x);
                begin = insert(begin, n, x);
                break;

            case 3:
                scanf("%d", &n);
                get(begin, n);
                break;
        }

        count--;
    }

    return 0;
}

Node *creat(int n) {
    int count = 0;
    Node *p1, *p2;
    p2 = malloc(len);
    p2->next = NULL;

    while (n) {
        p1 = malloc(len); 
             scanf("%d", &p1->date);
        p1->next = p2->next;
        p2->next = p1;
        n--;
    }

    return p1;
}

void output(Node *begin) {
    Node *p1 = begin;
    int flag = 0;

    while (p1) {
        printf("%d ", p1->date);
        p1 = p1->next;
        flag = 1;
    }

    if (flag == 0)
        printf("Link list is empty\n");
    else
        putchar('\n');
}

void get(Node *begin, int n) {
    Node *p1;
    p1 = begin;
    int i = 0;

    while (i < n - 1 && p1) {
        p1 = p1->next;
        i++;
    }

    if (i > n || p1 == NULL)
        printf("get fail\n");
    else
        printf("%d\n", p1->date);
}

Node *insert(Node *begin, int n, int x) {
    Node *front = NULL, *head, *move, *temp;
    head = move = begin;
    int i = 0;

    while (i < n - 1 && move->next) {
        front = move;
        move = move->next;
        i++;
    }

    if (move == NULL) {
        head = malloc(len);
        head->date = x;
        head->next = NULL;
    }

    if (move) {
        if (front == NULL) {
            head = temp = malloc(len);
            temp->date = x;
            temp->next = move;
        } else {
            temp = malloc(len);
            temp->date = x;
            front->next = temp;
            temp->next = move;
        }
    }

    return head;

}

Node *delet(Node *begin, int n) {
    Node *front = NULL, *move = begin, *head = begin;
    int i = 0, flag = 0;
    move = begin;

    while (i < n - 1 && move) {
        front = move;
        move = move->next;
        i++;
    }

    if (move == head && move) {
        head = head->next;
        flag = 1;
    } else if (move) {
        front->next = move->next;
        flag = 1;
    }

    if (flag)
        printf("delete OK\n");
    else
        printf("delete fail\n");

    return head;
}