SolarCity Interview Question: 1. About the projects that yo... | Glassdoor

Interview Question

Software Engineer Video Interview Interview San Francisco, CA

1. About the projects that you did. 2. If you need same

  database for 2 different applications how would you approach? 3. There are 10 stacks, each stack contains 10 bricks. Out of these 10 stacks.. one complete stack contains fake bricks and other 9 stacks has real bricks. Now when you take some collection of bricks (say 2 bricks from 1st stack, 3 from 4th stack, etc..) and weighing that collection of those picked bricks only once how would you identify which stack has fake bricks?? Note: Real bricks weighs 10 pounds and fake brick weighs 1 pound.

Interview Answer

1 Answer


1 brick from 1st stack
2 bricks from 2nd stack
3 from 3rd
4 from 4th
5 from 5th
6 from 6th.

So now if I take only bricks from the above mentioned 6 stacks in the above said manner.. And when we weigh this collection what the weight should be? if all bricks are real - the weight will come to 210 pounds.

if the weight is not 210 pounds then one of these stack has a fake brick.

if the weight is
201 pounds then it means only 1 brick is fake. That means we have taken only one brick from 1st stack. So as we came to know that only 1 brick is fake, then that would be 1st stack.

In the same way, if the weight is 192 pounds, then 2 bricks are fake. Which means the 2 bricks count is from 2nd stack. So 2nd stack is fake.

and so on..

Interview Candidate on Sep 17, 2015

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