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Welcome to techInterview, a site for technical interview questions, brain teasers, puzzles, quizzles (whatever the heck those are) and other things that make you think!

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### Chessboard

problem: using 31 dominoes, where one domino covers exactly two squares, can you cover all the empty squares on this chessboard (which has 62 spaces). if so, how? if not, why?

Notes: 3 notes

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### Easy River Crossing

Three cannibals and three anthropologists have to cross a river. the boat they have is only big enough for two people. if at any point in time there are more cannibals on one side of the river than anthropologists, the cannibals will eat them. what plan can the anthropologists use for crossing the river so they don’t get eaten?

remember! the boat can’t cross the river by itself, someone has to be in it to row it across.

a much harder river crossing problem will appear later this week.

`A - anthropologistC - cannibal++ - boat         riverAAA |============|    |++          |CCC |============| need to make it        river    |============| AAA    |          ++|    |============| CCC`

note that if you violate the “anthropologists > cannibals” rule at any point in time, it is illegal.. for example if a boat with a cannibal and an anthropologist travels to a shore with one cannibal on it, then # cannibals > # anthropologists, even if you say the anthropologist immediately takes the boat back.

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### Shapes

Part I: draw a square. divide it into four identical squares. remove the bottom left hand square. now divide the resulting shape into four identical shapes.

Part II: draw an equilateral triangle (all sides same length). divide it into four identical shapes. remove the bottom left hand shape. now divide the resulting shape into four identical shapes.

This is the sort of problem that i would expect on a MENSA test. i’m not too sure whether getting this right constitutes intelligence in a way that would benefit computer scientists, but maybe it does. if you figure it out, then you can say it does. if you can’t figure it out, then you can just say it’s all hogwash and it’s a stupid question.

Thanks to mark chesser

Notes: 1 note

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### Webloggers

Five webloggers - joshua Allen, meg Hourihan, jason Kottke, robert Scoble, and joel Spolsky - were competing for karma points on the major search engines: google, yahoo, altavista, lycos, and msn. karma was distributed on a five point scale. the most popular weblog received 5 points, and the least popular received 1 point. for each search engine, no two webloggers received the same number of points. overall scores were determined by adding up the individual scores from each search engine.

Allen got the highest number of karma points - 24. Kottke was consistent in his scores: he got the same karma points from 4 different search engines. Spolsky got 5 points from lycos, and 3 from msn.

no two webloggers got the same total score, and the final rankings were as follows: Allen, Hourihan, Kottke, Scoble, and Spolsky. how many karma points did Hourihan get from lycos?

Notes: 2 notes

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### Hard River Crossing

a disfunctional family has to cross the river. on one side of the river are a mom and 2 daughters, dad and 2 sons, the maid and the dog. there is a boat only big enough to hold 2 people (counting the dog as 1 person). only the adults are capable of operating the boat. everyone has to get to the other side, without anything bad happening.

difficulties: if the dog is left with anyone and the maid isn’t there to control him, he’ll bite. the dad can’t be left with any of the daughters when the mom isn’t there. likewise, the mom can’t be trusted alone with either of the sons when the dad isn’t there.

remember! only an adult can operate the boat, AND the boat can’t drive itself.

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### Classic Weighing

this is a classic problem which i have heard many times before. this is the “harder” of the two problems, since in this one, you do not know if the invalid item weighs more or less than the others.

solving it is only half the battle. writing up a solution that anyone including your grandma could understand, is very hard.

problem: the evil king from before sends his own assassin to take care of the evil queen who tried to poison him. of course, her trusty guards catch the assassin before any harm is done. the queen notices that the assassin is quite handsome and doesn’t really want to punish him by death. she decides to test his wisdom.

the queen gives the assassin 12 pills which are all completely identical in shape, smell, texture, size, except 1 pill has a different weight. the queen gives the man a balance and tells him that all the pills are deadly poison except for the pill of a different weight. the assassin can make three weighings and then must swallow the pill of his choice. if he lives, he will be sent back to the bad king’s kingdom. if he dies, well, thats what you get for being an assassin.

only one pill is not poison and it is the pill which has a different weight. the assassin does not know if it weighs more or less than the other pills. how can he save his skin?

Notes: 1 note

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### Monty Hall Problem

Another well known problem in probability is the Monty Hall problem.

You are presented with three doors (door 1, door 2, door 3). one door has a million dollars behind it. the other two have goats behind them. You do not know ahead of time what is behind any of the doors.

Monty asks you to choose a door. You pick one of the doors and announce it. Monty then counters by showing you one of the doors with a goat behind it and asks you if you would like to keep the door you chose, or switch to the other unknown door.

Should you switch? If so, why? What is the probability if you don’t switch? What is the probability if you do.

Lots of people have heard this problem.. so just knowing what to do isn’t sufficient. its the explanation that counts!

Notes: 1 note

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### Gold Chain

A man has a gold chain with 7 links. he needs the service of a laborer for 7 days at a fee of one gold link per day. however, each day of work needs to be paid for separately. in other words, the worker must be paid each day after working and if the laborer is ever overpaid he will quit with the extra money. also he will never allow himself to be owed a link.

what is the fewest # of cuts to the chain to facilitate this arrangement and how does that guarantee payment?

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### Surgeons

A one armed surgeon with a hand wound needs to operate on three patients. the surgeon only has two gloves. how can he operate on the three patients in turn without risking exchange of fluids? (remember he only has one arm so he only needs to wear one glove at a time.)

Notes: 4 notes

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### Clock

Part I: what is the angle between the minute hand and the hour hand at 3:15 on an analog clock? no, its not 0.

Part II: how often does the minute hand pass the hour hand on an analog clock?