Implementation of strlen function in three ways

There are three ways to implement the Strlen function:

First, the method of the counter

Second, the method of recursion

Third, the method of pointer minus pointer

Here are the implementations of the three methods:

Method of the counter:

int My_strlen (const char *STR)
{
ASSERT (str); Assertion to pointer to a string
int count = 0;
while (*STR)
{
count++;
str++;
}
return count;
}

Recursive method:

int My_strlen (const char *STR)
{
ASSERT (str);
if (*str = = ' + ')
return 0;
Else
Return 1 + my_strlen (str + 1);
}

Pointer minus pointer method:

int My_strlen (const char *STR)
{
ASSERT (str);
const char *p = str;
while (*p++)
{
;
}
return p-str-1;

Because *p== ' + ', then add 1, return to the next space ' \ ', causing the pointer to subtract one more element, so minus 1 to return the length of the string.
}

Implementation of strlen function in three ways