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Decode the Coding Interview in Java: Real-World Examples

Feature #14: Releasing Process Lock

Explore how to determine the process that failed to release a lock in operating systems by applying binary search on even indices of process logs. Understand the approach to efficiently analyze process lock and release sequences, enhancing your grasp of mutual exclusion in resource management.

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Description

Processes acquire and release locks on shared resources, which must be accessed with mutual exclusion. Whenever a process acquires a lock, the OS writes the corresponding process ID in a log file. Similarly, whenever the process releases the lock, the process ID is written to the log file again. Suppose that several processes acquired locks on a shared resource, but only one of these processes released the lock.

In this feature, we want to figure out which process did not release the lock. Each process is assigned a number, according to the order in which it acquired the lock. So, the first process that acquired the lock is given the number 1, the second process that acquired the lock is given the number 2, and so on. We will be given a list of integers, representing the order in which the lock was acquired and released. We have to return the process number that did not release the lock.

Let’s look at an example of this:

Solution

We will use binary search only on the even indices to solve this problem. First, we will set the following variables:

  • lo:
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