phobos-uplink

Your mission

Copy a command up to the probe only when every character of it is legal.

today's brief

September 2, 1988. A command sequence goes up to Phobos 1 on its way to Mars with one character wrong in it, and the software that would normally have caught that was not running, because the machine which checked uploads had been taken out of service. The bad command switched off the attitude control thrusters. The probe drifted off sun lock, the panels stopped pointing anywhere useful, and the batteries went flat. Nobody heard from it again. Refuse the bad upload before it goes.

See it in action

uplink(out, "ORBIT")

Expected result

5:ORBIT

Your checklist

For your own tracking. Tests grade your code.

cmd is a null terminated command word. A legal character is an uppercase letter, A to Z.
When every character is legal, copy cmd into out, write a null byte after it, and return how many characters were copied.
When any character is not legal, return -1 and leave out alone.
An empty command is legal and copies nothing.

More examples

uplink(out, "orbit")

Expected result

-1

uplink(out, "")

Expected result

0:

Constraints

Expected files

uplink.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions

phobos-uplink

Your mission

Copy a command up to the probe only when every character of it is legal.

today's brief

See it in action

uplink(out, "ORBIT")

Expected result

5:ORBIT

Your checklist

For your own tracking. Tests grade your code.

cmd is a null terminated command word. A legal character is an uppercase letter, A to Z.
When every character is legal, copy cmd into out, write a null byte after it, and return how many characters were copied.
When any character is not legal, return -1 and leave out alone.
An empty command is legal and copies nothing.

More examples

uplink(out, "orbit")

Expected result

-1

uplink(out, "")

Expected result

0:

Constraints

Expected files

uplink.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions