c 接口学习与实现

1.学习 strlen 函数

int strlen(const char * dest)
{
	char *p = dest;
	int n = 0;
	while( p[n] != '\0' )
		n++ ;
	return n;
}

2.学习 revert  函数

char * revert(char * dest)
{
	char * p = dest;
	int i;
	int n ;
	char c;
	n = strlen(p);
	for(i =0;i<n/2;i++)
	{
		c = p[n-1-i];
		p[n-1-i] = p[i];
		p[i] = c;
	}
	return dest;
}