C语言编程C++柔性数组结构示例讲解

#include<stdio.h>
#include<stdlib.h>
struct S
{
	int a;
	int arr[];//未知大小 柔性数组成员  数组的大小是可以调整的
};
int main()
{
	//我们怎么开辟呢
	//包含柔性数组成员的结构体的使用，要配合malloc这样的动态内存分配内存函数使用
	struct S* ps = (struct S*)malloc(sizeof(struct S) + 5 * sizeof(int));
	//我们如何使用呢
	ps->a = 100;
	int i = 0;
	for (i = 0; i < 5; i++)
	{
		ps->arr[i] = i;
	}
	//还想扩大呢
	struct S* ptr = (struct S*)realloc(ps, sizeof(struct S) + 10 * sizeof(int));//先交给ptr，防止内存调整失败
	if (ptr == NULL)//判断是否开辟成功
	{
		printf("扩容失败n");
		return 0;
	}
	else
	{
		ps = ptr;
		for (int i = 5; i < 10; i++)
		{
			ps->arr[i] = i;
		}
		for (int i = 0; i < 10; i++)
		{
			printf("%d ", ps->arr[i] = i);
		}
		//用完就释放
		free(ps);
		ps = NULL;
	}	
	return 0;
}

#include<stdio.h>
#include<stdlib.h>
struct S
{
	int a;
	int* parr;
};
int main()
{
	//我们怎么开辟呢
	struct S* ps = (struct S*)malloc(sizeof(struct S));
	//我们如何使用呢
	ps->a = 100;
	ps->parr = (int*)malloc(5 * sizeof(int));
	int i = 0;
	for (i = 0; i < 5; i++)
	{
		ps->parr[i] = i;
	}
	//还想扩大呢
	int* ptr = (int*)malloc(10 * sizeof(int));//先交给ptr，防止内存调整失败
	if (ptr == NULL)//判断是否开辟成功
	{
		printf("扩容失败n");
		return 0;
	}
	else
	{
		ps->parr = ptr;
		for (int i = 5; i < 10; i++)
		{
			ps->parr[i] = i;
		}
		for (int i = 0; i < 10; i++)
		{
			printf("%d ", ps->parr[i] = i);
		}
		//用完就释放
		free(ps->parr);
		ps->parr = NULL;
		free(ps);
		ps = NULL;
	}	
	return 0;
}