3i Infotech Placement: Sample Questions 446 - 447 of 1245

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Question 446

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Describe in Detail

Essay▾

What is the algorithm used in solving the 8 queens problem?

Explanation

Understanding of Backtracking
  • Backtracking is the type of the algorithm used in solving the 8 Queens problem.
  • Considers searching every possible combination in order to solve an optimization problem.
  • Also known as depth-first search.

Algorithm of backtracking:

  • Boolean solve (Node n)

    {

    If n is a leaf node

    {

    If the leaf is goal node, return true

    Else return false

    }

    Else

    {

    For each child c of n

    {

    If solve (c) succeeds, return true

    }

    Return false

    }

    }

  • The algorithm is expressed as a Boolean function.

Question 447

Question

MCQ▾

Semaphore is used for

Choices

Choice (4)

a.

dead-lock avoidence

b.

box

c.

synchronization

d.

None of the above

Answer

c.

Explanation

Understanding of Semaphore
  • Semaphore is a simple variable used which uses critical sections to achieve process synchronization in a multi-processing environment.
  • Two common semaphores are:
    • Counting semaphore which takes non-negative integer values
    • Binary semaphore which takes the value .
  • If semaphores are implemented using file descriptors. Semaphore creations are not atomic. Thus if two processes try to create, initialize and use a semaphore at the same time, a race condition is created.
  • They are thus implemented through interrupts or by using test-set operations to achieve atomicity

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