C语言：实现自定义strlen

strlen:计算字符串长度

#define _CRT_SECURE_NO_WARNINGS
#include 
//通过数组遍历计数
int mystrlen(char str[]) {
	int i = 0;
	while (str[i]) {
		i++;
	}
	return i;
}
//通过指针遍历计数
int mystrlen1(char* str) {
	int i = 0;
	while (*str) {
		i++;
		str++;
	}
	return i;
}
//对于数组来说两地址相减得到两地址之间的数组元素数目
int mystrlen2(char str[]) {
	char* p = str;
	while (*p) {
		p++;
	}
	return p-str;
}

int main(void) {
	char str[] = "hello";
	int ret = mystrlen(str);
	int ret1 = mystrlen1(str);
	int ret2 = mystrlen2(str);
	printf("ret = %dn", ret);
	printf("ret1 = %dn", ret1);
	printf("ret2 = %dn", ret2);
	return 0;
}