结构体动态数组,结构体与指针

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#include<memory.h>
#include<malloc.h>


struct csdn
{
    int id;
    int num;
};

void main()
{
    int num;
    scanf("%d",&num);
    struct csdn *p1 = malloc(sizeof(struct csdn)*num);// 堆上
    struct csdn *p2 = alloca(sizeof(struct csdn)*num);// 栈上
    memset(p1, 0, sizeof(struct csdn)*num);// 内存清0
    memset(p2, 0, sizeof(struct csdn)*num);// 内存清0

    printf("  p1     p2\n\n");
    for (int i = 0; i < num; i++)
    {
        printf("%d  %d  ,  %d  %d\n", p1[i].id = i, p1[i].num, p2[i].id = i, p2[i].num);
    }

    for (int i = 0; i < 10;i++)
    {
        int id;
        scanf("%d",&id);
        for (int j = 0; j < num;j++)
        {
            if (id == p1[j].id)
            {
                p1[j].num++;
                p2[j].num++;
                break;
            }
        }
    }

    printf("  p1     p2\n\n");
    for (int i = 0; i < num;i++)//动态数组引用方式
    {
        printf("%d  %d  ,  %d  %d\n",p1[i].id=i,p1[i].num,p2[i].id=i,p2[i].num);
    }

    free(p1);
    system("pause");
}

///////////////////////////////////////////////////////////////////////////////////

struct MyStruct
{
    int id;
    char str[10];
};
void main()
{
    //三种用途
    //struct csdn *p1 = malloc(sizeof(struct csdn)*num);//堆
    struct csdn *p2 = (struct csdn[]){ 1, 2, 3, 4 };

    printf("\n%d", p2[1].id);
    printf("\n%d", (&p2[1])->id);
    printf("\n%d", (p2 + 1)->id);//p[i] *(p+i)   &p[i]= p+i
    printf("\n%d", (*(p2 + 1)).id);//指针的形式

    //struct csdn  csdnx = { 10, 20 };
    //struct csdn  *p = &csdnx;
    //printf("\n%d", p->id);
    //printf("\n%d", (*p).id);

    system("pause");
}

void main()
{
    struct csdn csdndata[100];  //int a[100]
    struct csdn *p3 = csdndata;//int *p

    struct csdn csdndataX[10][10];  //int a[10][10]
    struct csdn(*p4)[10] = csdndataX;//int (*p)[10]=malloc(sizeof(int)*100)

    struct csdn(*p5)[10] = malloc(sizeof(struct csdn) * 50);//
    p5[3][4];
}