Top 10 Puzzles, Riddles, Logical and Lateral Thinking questions asked in Programming Job Interviews

Puzzles, riddles, logical questions, and lateral thinking questions are
integral part of any programming job interviews. I missed to include some
puzzles, when I shared my list of top 30 programming interview questions
earlier, and couple of my friends requested to share some puzzles as well.
These puzzles and lateral thinking questions are mostly collected from various Java programming interviews on
Investment banks, but they are equally useful to any programming job
interviews. I have seen more puzzles and logical questions at junior level i.e.
2 to 4 years. These kinds of puzzles, if asked at the beginning of interview,
can make or break the interview. It’s not easy to solve them, especially when
you see them first time, but what is surely not to do is give up without try,
even if you can't think of answer, try to show rational approach. Remember it's OK, if you don't answer any puzzle question, but your approach towards unknown
problem get noticed. At the same time lateral thinking questions offers several
answers, and you can give your own explanation as well, but make sure it must
look genuine and seems logical. Puzzles and riddles also forms a big chunk of
Microsoft and Google Interview questions as
well, and they are some really nasty and tough to answer. Anyway, I have not
provided answers of these puzzles and logical questions, so that you can at
least give it a try. Immediate answers kill the purpose of puzzles and riddles,
and it's fun to solve them by yourself. By the way, you can easily find answers
of these puzzles using Google, as they have asked numerous times on various
programming interviews on software and technology companies.

10 puzzles, riddles, logical and lateral
thinking question

Here is my list of 10 riddles,
puzzles, logical and lateral thinking questions. Try to solve it by
yourself before searching for answers in Google, they are not that tough or
difficult. Easy answers spoils purpose of puzzles, so don’t look at them, until
you are going for interview very next day.

1) There are 27 coins and a two-pan balance. All coins has same weight
except for one, which is heavier than all others. All coins looks identical.
What is the minimum number of weighing required to certainly find out heavier
coin?

2) There are two sticks which takes one hour to burn from one end to
other. The sticks do not burn at a constant rate i.e. some part may burn faster
than others. You need to measure 45 minutes by using these two sticks and a
lighter.

3) Two persons are walking into a railway tunnel. Upon crossing 2/3rd of
the tunnel, they saw train is coming from opposite direction. Each person ran
for a different end of tunnel with speed of 10 km per hour. Fortunately, both
persons escaped from the tunnel just right time i.e.. at the time train would
have run through them. Assuming train was running with a constant speed and
both persons reacted immediately, Find out speed of train.

4) There are thee switches outside of a closed room to operate three
different light bulb inside the room. You can only go into the room once and
you need to determine which switch belongs to which bulb. Just to make it
clear, room is perfectly locked and its not possible to determine whether
lights are on from outside the room.

5) You have 10 Jars filled with marbles. Each marble weighs 10 gm, except
one Jar which contains defective marbles which weighs 9 gm. Given a scale to
weigh, How do you find Jar with defective marbles in just one measurement. Here
scale is modern day electronic scale to measure weight.

6) A person shoots her wife. Then holds her under water for 5 minutes.
Finally, he hangs her. But after 10 minutes they both go out together and enjoy
a wonderful dinner together. How can this be?

7) A father and son are going in a car and suddenly there car met
accident. Father died on the spot but the child rushed to the hospital. When he
arrives in the hospital, doctor says, "I can't operate on this child, he
is my son!" How can this be?

8) You have a 5 liter Jug and a 3 liter Jug and unlimited supply of
water. You need to measure exactly 4 liter of water but there is no measuring
instrument or cup. Also Jugs are oddly shaped and doesn't contain any mark.

9) There are Four people needs to cross the bridge during night. The
bridge can hold the weight of two people at a time and can not be crossed
without a torch. Each person walk with different speed, first can cross the
bridge in 1 minutes, second in 2 minutes, third in 5 minutes and fourth take 10
minutes to cross the bridge. If two persons go together, they walk with the
speed of slower person. What is the least amount in which all four people cross
the bridge.

10) A person's age is many days as his father's age in weeks and as many
month as his grand father's age in years. If you combine age of all three it
comes 120 years. What is the age of all three?

That's all on this list of top 10 puzzles, riddles, logical questions
and lateral thinking questions asked in programmer interviews. These
question has maximum impact when programmer doesn't heard about it, and it
means they may appear differently in actual interview. As a candidate, you can
prepare all these question to get your mind working and knowing some techniques
to solve them, but be prepare for surprise in actual Interview. Key of solving
puzzles, logical questions or riddles are keeping your cool and not panicking.
Even if you don't know answer you should start explaining your way and logic
and if you have any answer which is out of box then better say it. Many times
it happen when candidates are selected even if they don't solve the puzzles but
in the process show some promise.

Source:http://javarevisited.blogspot.com/2013/04/top-10-puzzles-riddles-logical-programming-question-lateral-thinking-interview.html