Is it a private (RFC1918) address?

Challenge

Recognise the RFC 1918 private ranges — the only addresses a home lab should ever target.

Task

Implement int is_private_ip(int a, int b) that returns 1 if an address whose first two octets are a.b is in a private range, else 0.

Private ranges (based on the first two octets):

• 10.x (first octet 10)
• 192.168.x (192 then 168)
• 172.16.x .. 172.31.x (172 then 16..31)

Input

• a, b: the first and second octets of the address. The grader passes fixed values.

Output

Returns int: 1 if a.b falls in a private range, else 0.

Example

is_private_ip(10, 0)     ->   1
is_private_ip(192, 168)  ->   1
is_private_ip(172, 20)   ->   1
is_private_ip(8, 8)      ->   0   (public)
is_private_ip(172, 15)   ->   0   (just outside 172.16-31)

Edge cases

• 172 is private only when the second octet is 16..31.

Rules

• Pure arithmetic on the two octets.

Input format

The first two octets a, b of an address.

Output format

An int: 1 if a.b is in a private (RFC 1918) range, else 0.

Constraints

10.x; 192.168.x; 172.16-31.x; second octet matters for 172.

Starter code

int is_private_ip(int a, int b) {
    /* TODO */
    return 0;
}