Apparent Microsoft interview question

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Can You Figure This One Out ???

Allegedly, this is one of the questions for potential Microsoft employees. I must warn you, you can really get caught up trying to solve this problem. Reportedly, one guy solved it by writing a C program, although that took him 37 minutes to develop (compiled and ran on the 1st try though).

Another guy solved it in three minutes. A group of 50, at Motorola, couldn't figure it out at all. See how long it takes you.

Here we go...

"U2" has a concert that starts in 17 minutes and they must all cross a bridge to get there. All four men begin on the same side of the bridge. You must help them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them.

The flashlight must be walked back and forth, it cannot be thrown, etc.
Each band member walks at a different speed. A pair must walk together at the rate of the slower man's pace:

* Bono: - 1 minute to cross
* Edge: - 2 minutes to cross
* Adam: - 5 minutes to cross
* Larry: - 10 minutes to cross

For example: if Bono and Larry walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Larry then returns with the flashlight, a total of 20 minutes have passed and you
have failed the mission.

Notes: There is no trick behind this. It is the simple movement of resources in the appropriate order.

There are two known answers to this problem. This is based on a question that Microsoft gives to all
prospective employees.

 

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I'm a bit tired but here's some theory.

So if I'm helping them then I can walk them.

So I'd walk Larry across in ten mins.
Then Adam would walk across.5 mins.
Then I'd give Bono the flashlight and he'd walk with the Edge.2mins.

= 17 mins.

-------------------------
second theory is that it says "they must all cross a bridge," but it doesn't say the same bridge.

So they may each cross there own bridge, witht heir own flashlight, therefore it would take 10 mins.

----------------------

Still thinking

 

Ah, another theory.

It says they must all cross a bridge.So, if the goal is to cross a bridge, then here's how:

Bono walks with Larry 10 mins
Bono walks back 1 min
Bono gives the flashlight to the Edge and Adam 5 mins

= 16 mins.

And they've all crossed the bridge.

Nah, maybe :roll:

 

By jove I think I've got it

Bono and the Edge walk across 2mins
The Edge walks back 2mins.
The Edge gives the flashlight to Adam who walks across with Larry.10mins.
Larry gives the flashlight to Bono who walks across.1min.
Bono walks across with the Edge.2mins.

Total = 17 mins.

YES

Darn, took me an hour, but at least I'm better than 50 motorola workers

 

By jove I think you have it flex.

Pure for the motorola workers.

 

MY response

Don't care - not a U2 fan!!

 

Nice one Flex - it had me stumped

 

Can't be done. Can't be done. Oh, Flex did it. Damn.