Re: Logic Quiz
^lol...life on that island was boring anyway. They couldn't communicate with one another.
Re: Logic Quiz
I had another full explanation but it logged me out.
In short all the blue eyed people leave on the third night.
my explanation not sure if I'm gonna bother now ... It was so long.
but it is to do with how they each put themselves in the other persons shoes. The Guru and her statement is important.
Re: Logic Quiz
Guru says she sees a blue eyed person
If Guru said she sees a non-blue eyed person each person would conclude it was them and not rush to boat that very evening.
But instead she said the opposite. Now each other islander sees at least one non-blue eyed person ... If anyone saw two or more non-blue eyed people they would correctly conclude their own eyes to be blue and leave that evening.
Seeing everyone return back to the island the next day proves to the Guru that no one can see two or more non-blue eyes. She herself sees no non-blue eyes and hence concludes her own eyes to be non-blue.
she does not attenpt to leave on night two because she can't anyway being a non-blue eyed gal.
this triggers all the other islanders to conclude that they each have blue eyes and they all leave on night 3 because they realise the Guru's inaction on night 2 means that she sees 100 pairs of blue eyes.
The Guru is left alone on the island.
Re: Logic Quiz
^ but every one know every ones eye color but their own.
So every one knows 99 ppl are BE(blue eyed)
She says she see or say there is only 1.
So she wrong about 98 people. almost 99%.,every one know that.
So 99% chance is she is wrong about me too(this is the dude thinking about leaving)
So almost 99% chance is every one would leave first night.
That if they are driven with logic.
PS: that if they are not computer science ppl. Computer science ppl would stay, and ask for another quiz.
Now what did I win ?
Re: Logic Quiz
^ but every one know every ones eye color but their own.
Initially yes ... But based on their attempt to go or not there is a way to deduce the colour of their own eyes I thought my explanation makes that clear. Read it slowly Monk ...
Re: Logic Quiz
Look:
Guru sees- 0 non-blue eyed people and 100 blue eyed people
Others see- 99 blue 1 non-blue
If Guru saw 1 or more non-blue then Others would conclude there must be two or more non-blues because they already see Guru with non-blue ... If they see 2 or more non-blue then they work out that they must be blue eyed. So all people who see 2 or more non blue would leave ... But since they don't see that, they don't leave ... them not leaving indicates she is the only non-blue eyed person. When she does not attempt to leave that action tells the others also that there is only one non-blue eyd person.
Re: Logic Quiz
Look:
Guru sees- 0 non-blue eyed people and 100 blue eyed people Others see- 99 blue 1 non-blue
If Guru saw 1 or more non-blue then Others would conclude there must be two or more non-blues because they already see Guru with non-blue ... If they see 2 or more non-blue then they work out that they must be blue eyed. So all people who see 2 or more non blue would leave ... But since they don't see that, they don't leave ... them not leaving indicates she is the only non-blue eyed person. When she does not attempt to leave that action tells the others also that there is only one non-blue eyd person.
"Everyone can see everyone else at all times and keeps a count of the number of people they see with each eye color (excluding themselves),"
You would be right if this was not one of the condition/situation.
Re: Logic Quiz
"Everyone can see everyone else at all times and keeps a count of the number of people they see with each eye color (excluding themselves),"
You would be right if this was not one of the condition/situation.
The condition says they can't see their own eye colour ... But it does not say that they can't deduce their own eye colour. The question also says if any islander can figure out their own eye colour and that it is blue they will go home.
Re: Logic Quiz
^ but every one know every ones eye color but their own.
So every one knows 99 ppl are BE(blue eyed) *She says she see or say there is only 1. * So she wrong about 98 people. almost 99%.,every one know that. So 99% chance is she is wrong about me too(this is the dude thinking about leaving) So almost 99% chance is every one would leave first night.
That if they are driven with logic.
PS: that if they are not computer science ppl. Computer science ppl would stay, and ask for another quiz.
Now what did I win ?
I thought she said she sees at least one
Re: Logic Quiz
^ but every one know every ones eye color but their own.
So every one knows 99 ppl are BE(blue eyed) She says she see or say there is only 1. So she wrong about 98 people. almost 99%.,every one know that. So 99% chance is she is wrong about me too(this is the dude thinking about leaving) So almost 99% chance is every one would leave first night.
That if they are driven with logic.
PS: that if they are not computer science ppl. Computer science ppl would stay, and ask for another quiz.
Now what did I win ?
she didn't say "there is only 1", she says "she sees blue eyed people" ... see the question again.
Re: Logic Quiz
The condition says they can't see their own eye colour ... But it does not say that they can't deduce their own eye colour. The question also says if any islander can figure out their own eye colour and that it is blue they will go home.
Bingo, as the question states that they are perfect logicians
Re: Logic Quiz
Everybody knows that one. You feed the cabbage to the goat, goat to the wolf, load up the boat and cross.
Re: Logic Quiz
Alright guys ... I guess its time to explain. couple of guys almost had the correct answer though their explanation wasn't "logical". I will update this post after sometime to list those name who had the correct answer.
now lets talk about the answer.
You can related these questions to mathematical induction in which you need to prove it for k and then k+1 ... and the rest is proven automatically. In pure CS terms, you need to break down this problem to 3 boundaries.
- What if there is no blue eye people
- What if there is one blue eye people 2.a what if there are two blue eye people
- based on 2, and 2.a you can deduce what if there are N blue eye people
**
Case 1
**What if there is no blue eye people, so the guru says "I don't see any blue eye" ... kahani khatm!
Case 2
What if there is one blue eye person. The guru says, "she see at least 1 blue eye person". Now the blue eye person can see rest of the 99 people and all of them are brown eyes. Given that Guru sees one blue eye, he can logically deduce that he is the one Guru is talking about. So he leaves at first night (number of blue eye people = 1 .... he left at 1 night)
**Case 2.a
**What if there are two blue eye person. The guru says, "she see at least 1 blue eye people". Now the first blue eye person see that there are 98 brown eye , 1 blue and and then him. He assumes, that the blue eye person would leave tonight (see Case 2). Same goes for the other blue eye person, he would assume that the first blue eye would leave tonight (see case 2) but both of them didn't. Which leads them to logically deduce that they see "another" blue eye person and they want to make sure. On the second day, the guru says the same thing (this is almost useless here) ... But tonight they can make the decision since they know the other blue eyed person didn't leave, so it must be him which is also blue eye. So both of them would leave on night 2. (number of blue eye people = 2 .... they left at 2 night)
**Case 3
**From case 2 and 2.a you can deduce that given that there are N blue eye people at the island, they will leave at Nth night which would be 100 in this case.
Re: Logic Quiz
But then her statement doesnt add to any thing.
Since they all see 99 blue eyed people.
As a matter of fact if she had said I see 99 blue eyed people every one would have stayed thinking they are the only one with non-blue eyes.
Also if her statement does not add to solution, then its a trick question… MQ:nahi:
Re: Logic Quiz
I must have read the riddle wrong. I didn’t know there were brown eyed people on the island. 
Re: Logic Quiz
They just came now to fix the issue, guru created.
Re: Logic Quiz
no … it wasn’t. the guru clearly states “I see a blue eye person” she never stated a number or whatsoever. Given that everyone is a logical person on the island, they know what this statement means. So they are actually inducing everything from the day 1 … as i mentioned in my answer that her statement on second day wouldn’t mean much.
Re: Logic Quiz
anyway, who is asking next question ... or shall i ask another one ? (next one would be easy though)
Re: Logic Quiz
**Alright guys - here is one of the toughest one that i know. Its a very popular interview question for CS students so you can google the answer but it all depends on you if you want to be honest or just win. I have made some changes to the riddle to make it easy and less complex.
**A group of people with blue eye colors live on an island. They are all perfect logicians -- if a conclusion can be logically deduced, they will do it instantly. No one knows the color of their eyes. Every night at midnight, a ferry stops at the island. Any islanders who have figured out the color of their own eyes and if their eye-color is blue then they can leave the island, and the rest stay. Everyone can see everyone else at all times and keeps a count of the number of people they see with each eye color (excluding themselves), but they cannot otherwise communicate. Everyone on the island knows all the rules in this paragraph. On this island there are 100 blue-eyed people and the Guru (she happens to have green eyes). So any given blue-eyed person can see 99 people with blue eyes (and one with green), but that does not tell him his own eye color; as far as he knows the totals could be 99 blue and 1 not blue. The Guru is allowed to speak once (let's say at noon), on one day in all their endless years on the island. Standing before the islanders, she says the following: "I can see someone who has blue eyes." Who leaves the island, and on what night? There are no mirrors or reflecting surfaces, nothing dumb. It is not a trick question, and the answer is logical. It doesn't depend on tricky wording or anyone lying or guessing, and it doesn't involve people doing something silly like creating a sign language or doing genetics. The Guru is not making eye contact with anyone in particular; she's simply saying "I count at least one blue-eyed person on this island who isn't me."
The Guru gets to leave. When she says I can see at least one person with blue eyes that isn't me, that implies she is saying she also has blue eyes.
Since the group is logical and instant pus in their logic, all the 100 blue eyed people shout "but your eyes aren't blue. They are green".
Now the guru knows her eye color. And she gets off the island.
Re: Logic Quiz
happens with the color-blind ppl 