Write your own code simulates implement strlen function function

I, entitled

Write your own code simulates implement strlen function function (for strings). (Of course, the normal time is not recommended to write the function, find the string length strlen function called directly on it.)

Second, the code implements (three methods)

#include<stdio.h>
#include<Windows.h>

int my_strlen1(const char * str)//计数器方式
{
	int count = 0;
	while (*str)
	{
		count++;
		str++;
	}
	return count;
}
int my_strlen2(const char * str)//递归方式，不能创建临时变量计数器
{
	if (*str == '\0')
		return 0;
	else
		return 1 + my_strlen2(str + 1);

}
int my_strlen3( char * str)//指针方式
{
	char *p = str;
	while (*p != '\0')
		p++;
	return p - str;
}


int main()//模拟实现strlen函数
{
	char str[] = "asdfgfhgj";
	printf("first way:%d\n",my_strlen1(str));
    printf("second way:%d\n", my_strlen2(str));
	printf("third way:%d\n", my_strlen3(str));
	system("pause");
	return 0;
}