#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include<stdlib.h>

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

node* create(int data) {
	node* newnode = malloc(sizeof(node));
	newnode->data = data;
	newnode->next = NULL;
	return newnode;
}

void insert(int data, node** head) {
	node* newnode = create(data);
	if (*head == NULL) {
		*head = newnode;
	}
	else {
		newnode->next = *head;
		*head = newnode;
                //只改了这里的两行代码
	}
}

void show(node* head) {
	while (1) {
		printf("%d", head->data);
		if (head->next == NULL) {
			break;
		}
		head = head->next;
	}
}

int main() {
	int a = 1, b = 2, c = 3;
	node* head = NULL;
	insert(a, &head);
	insert(b, &head);
	insert(c, &head);
	show(head);
	return 0;
}

//PS：在主函数里面的head初始化为NULL就行了，别也动态分配内存，这样只分配了内存但没有初始化为NULL，insert函数不好找尾节点，而且在主函数对head进行动态分配没啥用，让他默认为空指针就行了