C语言—函数、数组和指针

作者：追风剑情发布于：2019-10-8 19:56 分类：C

示例

//Visual Studio中加上这句才可以使用scanf()
//否则只能使用scanf_s()
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdbool.h>

#define SIZE 10

int sum(int ar[], int n);
//等价形式
//int sum(int *ar, int n);
//int sum(int *, int);
//int sum(int [], int);

//int sump(int *ar, int n);

//argc: 参数个数 argv[]: 参数数组
int main(int argc, char *argv[])
{
	int marbles[SIZE] = {20,10,5,39,4,16,19,26,31,20};
	long answer;
	answer = sum(marbles, SIZE);
	printf("The total number of marbles is %ld.\n", answer);
	printf("The size of marbles is %zd bytes.\n", sizeof marbles);

	system("pause");
	return 0;
}

int sum(int ar[], int n)
{
	int i;
	int total = 0;
	for (i = 0; i < n; i++)
		total += ar[i];
	//如果编译器不支持zd%，可用%u或%lu代替
	//这里的ar是一个指向数组的指针,sizeof ar计算的是这个指针所占字节数
	printf("The size of ar is %zd bytes.\n", sizeof ar);
	return total;
}

//等价形式
/*int sump(int *ar, int n)
{
	int i;
	int total = 0;
	for (i = 0; i < n; i++)
		total += ar[i]; //arr[i]和*(ar+i)相同
	return total;
}*/

运行测试

示例：使用指针形参

//Visual Studio中加上这句才可以使用scanf()
//否则只能使用scanf_s()
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdbool.h>

#define SIZE 10

int sump(int * start, int * end);

//argc: 参数个数 argv[]: 参数数组
int main(int argc, char *argv[])
{
	int marbles[SIZE] = {20, 10, 5, 39, 4, 16, 19, 26, 31, 20};
	long answer;
	answer = sump(marbles, marbles + SIZE);
	printf("The total number of marbles is %ld.\n", answer);

	system("pause");
	return 0;
}

int sump(int * start, int * end)
{
	int total = 0;
	while (start < end)
	{
		//total += *start;
		//start++; //指针移向下一个数组元素

		//与上面两句等效，*与++优先级相同
		total += *start++;
	}
	return total;
}

运行测试

示例：一元运算符*与++优先级相同

//Visual Studio中加上这句才可以使用scanf()
//否则只能使用scanf_s()
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdbool.h>

int data[2] = {100,200};
int moredata[2] = {300,400};

//argc: 参数个数 argv[]: 参数数组
int main(int argc, char *argv[])
{
	int *p1, *p2, *p3;
	p1 = p2 = data;
	p3 = moredata;
	printf("*p1=%d, *p2=%d, *p3=%d\n", *p1, *p2, *p3);
	printf("*p1++=%d, *++p2=%d, (*p3)++=%d\n", *p1++, *++p2, (*p3)++);
	printf("*p1=%d, *p2=%d, *p3=%d\n", *p1, *p2, *p3);

	system("pause");
	return 0;
}

运行测试