Facebook Software Engineer Interview

The minimum number is 1.

The answer is 10.

Minimum is 1...in the off chance the answer is 1 or 1000 and you guess 2 or 999.

The MINIMUM is one. If my first guess is 2 and you say lower, I have determined the number must be 1. Same with 999 and higher.

You could always guess it on the first go. A better question would be "What is the most efficient way to guess a number between 1 and 1000, given that you'll be told higher or lower each time"

This is a binary search where the answer solves the equation 2^x=500
X=ln500/ln2= 6.214608/0.693147=8.965784. So the answer is 9.

Tells you what happens when someone tries to be cute with interview questions, but doesn't say it correctly. It should be "What is the minimum number of guesses that you need to GUARANTEE finding the correct number in all times you try?" '1' obviously wouldn't cut it. 10 is all I need.

Think of it this way. You have a string of 1000 Christmas lights (no religion-slamming on Christmas - not the point), and they're the old kind that requires all bulbs to be working for the whole string to work. The string goes out. Assuming that only one bulb burned out, they're small so you can't just look at the bulb to see if it's burned out or not, and you really don't want to be standing out in the cold for a long time finding the bulb, it really helps to remember this binary-search rule. Instead of up to 1000 bulbs to check, you only need to check up to 10.

Bob, you're close. It's 2^x = 1000, not 500.

Minimum is 1 if you are lucky and guess right first try by chance. One could also propose a search scheme, but as stated there is no efficient search scheme. One might think you could use bisection - guess 500 then 750 or 250 etc. But that will not work here since the number can be any irrational real number not just whole numbers. Thus there are infinite numbers between any two numbers so you can never narrow the search. Sorry!

if you cut 1000 in half 9 times you end up with 2 (1.9531) so the answer is 10. don't over think it, it's not 1 it's 10

elementary my dear......

I guess that's one of those questions meant to see if you pay attention.

However I would expect a facebook interviewer would want you to recognise the binary-tree search question. So after you answer 1, you'll be asked to find 10. I would've said ln(1000) so it's 10.

Sorry: ln(1000)=7 so I'd said 7. Yet it's 10 worst case:

1000
500
250
125
63
32
16
8
4
2

Jim is wrong the answer is not 10! He is making assumptions that are given in the problem statement. Nothing says you are searching for a whole number. If you like I will select a number between 1 and 1000, I'll give you 100 guess, I assure you, you will not get the answer.

My 13 year old son understands this problem. Woe is the world if people don't understand this.

the minimum guess is 1
the maximum guess is 9

in case of the can guess the correct answer at the first time, then the minimum guess is 1

but the maximum guess is like what bah said

but, you forgot something. That you will NEVER choose 1,000 for the first guess

your first guess would be 500.