Puzzle Post 5

[Wol]

ronin friendly spoiler:

Spoiler

Solution 1: The lamp is being run from a supply which doesnt have an electricity meter.

Solution 2: The room is soundproof, and you have no klaxon. You can't determine what is "off" and "on" on the switches. Theres no label showing on and off

Solution 3: You're very nearly there, but not quite. Try doing it without setting the place on fire

You've pretty much written the answer in your list of facts, you just need to elaborate it into a test case.


"one input and one output that can be tested." <<<

 

[Ronin Storm]

The spoilers blocks almost need a preview on what level of spoiling they do.

 

[Wol]

Edited previous post

I want to not spoil it for others just coming into the thread, e.g. spoiling it the same level as you'd put spoilers around your three possible solutions.

 

[Ronin Storm]

Ah super, thanks. Spoiler read and noted. I'll go and muse some more.

Also:

Totally don't understand how so many of you have immediately got the "obvious" answer. Sort of feel like I've solved the puzzle a few times over now, but arbitrary constraints mean my answer is wrong.

 

[Wol]

The obvious answer would be to ask your mate dave to shout out of the door when the light turns on But as you say, stupid constraints. But then it wouldn't be a riddle

You're pretty much there with your list of facts and solution 3. As D says, do solution 3, but without setting stuff on fire!

 

[Ronin Storm]

Here's a question:

Is the lightbulb in a known state to start with?

 

[thatbloke]

The bulb starts in the "off" setting

 

[Ronin Storm]

In that case:

Solution 4: (aka The Comparison Solution)

Spoiler

Assuming the bulb is off to start with, flip all switches and leave for 5 minutes.
Alternatively, if the bulb is on to start with, flip all switches and leave for an hour, then flip all switches and leave for 5 minutes.
Turn each switch off, leaving around 2 minutes between each flip. Total time between first and last flip is 4 minutes.
Enter room and touch lightbulb (carefully).
If the bulb is very hot (seconds cooling), it was switch 3.
If the bulb is less hot (2 minutes cooling), it was switch 2.
If the bulb is merely warm (4 minutes cooling), it was switch 1.

This solution relies on the bulb being in a known state to start with. If the bulb is an unknown state, this solution fails.

 

[Ronin Storm]

Oh, and the other solution I thought of, which is almost certainly wrong (by this puzzle's definition):

Solution 5: (aka The Flash Test)

Spoiler

Light switches sometimes spark on creating a live circuit.
Two switches cannot make a circuit as they have no devices to complete their circuit.
Turn off all lights in the corridor.
Twiddle each switch quickly and watch for sparking behind the lighting panel.
The switch that sparks is the one that controls the light.

However, the light isn't guaranteed to still be working after this test.

 

[thatbloke]

In that case:

Solution 4: (aka The Comparison Solution)

Spoiler

Assuming the bulb is off to start with, flip all switches and leave for 5 minutes.
Alternatively, if the bulb is on to start with, flip all switches and leave for an hour, then flip all switches and leave for 5 minutes.
Turn each switch off, leaving around 2 minutes between each flip. Total time between first and last flip is 4 minutes.
Enter room and touch lightbulb (carefully).
If the bulb is very hot (seconds cooling), it was switch 3.
If the bulb is less hot (2 minutes cooling), it was switch 2.
If the bulb is merely warm (4 minutes cooling), it was switch 1.

This solution relies on the bulb being in a known state to start with. If the bulb is an unknown state, this solution fails.

That pretty much nails it, but there is a slightly more elegant solution that takes a bit less time to figure out

 

[Wol]

Solution 4 is pretty much there.

take that idea, and go back to your list of facts where you mentioned things you can measure.....

 

[Ronin Storm]

Right, so I've solved the problem but not efficiently enough?

I've said it elsewhere, but I hate this puzzle and it hates me. Die puzzle die!

When you say "more elegant", is it that the full solution takes less than 4 minutes? i.e. it might just be a single check?

 

[Wol]

Right, so I've solved the problem but not efficiently enough?

Could you tell between "less hot" and "merely warm"? I probably couldn't, so wouldnt know if it was switch 1 or 2.

ronin friendly:

Spoiler

What things can you check about the lightbulb?

You shouldn't need to use some form of distinction between "merely warm" and "less hot". You should be working on a binary solution for the thing you measure e.g. its one, or t'other, rather than ternary: hot, less hot, merely warm

 

[Ronin Storm]

Response to Wol's points, spoilered to keep the thread relatively pure:

Spoiler

Binary states, hmm?

Hot - Cold
Lit - Dark
Consuming - Idle

The glass of the bulb gives me a measure of heat after the bulb has gone out but checking only once gives me a trouble and prevents me making an assessment on that alone...

*muses*

Okay, I have it, I believe, fairly elegantly this time:

Solution 6: (aka The "I Kill You In Code" Solution)

Spoiler

if (bulb.state == off)
{
  switch1.toggle();
  wait(1);
  switch1.toggle();
  switch2.toggle();
  room.check();
  if (bulb.lit == true)
  {
    return switch2;
  }
  else if (bulb.temperature == hot)
  {
    return switch1;
  }
  else
  {
    return switch3;
  }
}

 

[Wol]

waheh! there we go!

 

[elDiablo]

Solution 6: (aka The "I Kill You In Code" Solution)

Spoiler

if (bulb.state == off)
{
  switch1.toggle();
  wait(1);
  switch1.toggle();
  switch2.toggle();
  room.check();
  if (bulb.lit == true)
  {
    return switch2;
  }
  else if (bulb.temperature == hot)
  {
    return switch1;
  }
  else
  {
    return switch3;
  }
}

Dear Sir,

I find your method of posting amusing. Thank you.

Yours faithfully,
elD

 

[Tetsuo_Shima]

You win!