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Logic Interview Questions


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Logic Interview Questions

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You have 25 horses, what is the minimum number of races you can find the top 3. In one race you can race 5 horses, and you don't have a timer.

29 Answers

I don't know, but Google it, you'll find the answer. Once you know it, it's obvious.


Probably 8. First answer: at least 5 (you have to look at every horse). Second answer: 11. You can race five horses, replace 4th and 5th place horse by two horses from pool of horses that haven't raced, and continue doing this until all horses have raced. Since there are 25 horses, you need 1 race for the first five horses and 10 to go through the remaining 20. Third answer: 8. Round 1 (5 heats) : Race horses in heats of five. Eliminate all 4th and 5th place horses. (15 horses left) Round 2 (1 heat): Race winning horses from every heat. Eliminate 2nd and third place horses that lost to horses in round 2 that came third or worse. (7 horses left). Round 3 (1 heat): Pick any five horses. Race them. Eliminate bottom two and replace with remaining two horses. (5 horses left) Round 4 (1 heat): Eliminate bottom two. Note: after round 2 it may be possible to use some interesting decision tree mechanism to determine the three fastest horses using fewer horses per heat but you still need two heats to do that. This problem assumes horses don't get tired, no ties are possible and a horse's speed is deterministic race after race after race. Good assumptions for brain teasers, but not for real life.

25 racehorses, no stopwatch. 5 tracks. Figure out the top three fastest horses in the fewest number of races.

9 Answers

You are in a room with 3 switches which correspond to 3 bulbs in another room and you don't know which switch corresponds to which bulb. You can only enter the room with the bulbs once. You can NOT use any external equipment (power supplies, resistors, etc.). How do you find out which bulb corresponds to which switch?

6 Answers

Given a set of people, one of them is a celebrity. You have a 2D array which describes which people know each other, that is [N, M] is true if N knows M. The celebrity will not know anyone (except them self) and everyone will know the celebrity. Find an order N algorithm to find the celebrity.

5 Answers

If you have a three gallon jug and a five gallon jug No marks on either one The goal is to fill the five gallon jug with four gallons of water How is this accomplished?

5 Answers

Considering a 2-dimension matrix that can only be traversed by 1 adjacent position at a time and never diagonally. Create an algorithm to traverse that matrix from its upper-left corner to its lower-right corner using the shorter possible path in the most efficient way.

5 Answers

Scenario: You have 8 golf balls and 1 is heavier than the 7 others. All you have is a balance used in chemistry classes. What is the shortest number of times you could measure the golf balls to find the heaviest ball?

5 Answers

We have a pond containing a single bacterium. The number of bacteria double every 5 minutes, and the pond is full of them in 24 hours. If we started with the same pond but two bacteria, how long will it take to fill the pond?

4 Answers

There is a body of water that starts with 1 square unit, and doubles in size every day (2 units after 2 days, 4 units after 4 days). It takes 100 days to fill up. How many days would it take to fill if you started with 2 square units?

6 Answers

Sequence of numbers in random order and 1 of them is missing how to find that out...

5 Answers
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