Question

Hi how does this code work'?njobs is the number of jobs in queue?? how can we add a job in queue in priority order?

// add a new job to the queue in priority order void addToQ(JobQ *g, Job j) assert( != NULL); int i, ki for (i = 0; i < q->njobs; i++) if () .priority > .->jobs[i].priority) break; for (k = q->njobs; k > i; k--) q->jobs[k] = q->jobs [k-1]; q->jobs[i] = j; q->njobs++;

Answer 1

The addToQ method adds Job j to the Job Queue q keeping in mind the priority of the job.

1. Firstly, the assert function checks whether the job is empty of not.
2. If the job queue is not empty, the for loop iterates to an index "i" in the job queue until it finds a job whose priority is less than the priority of the job to be added. Also, this is the index where the new job is to be added since all the elements in the queue starting from this index i.e (i) till the end have less priority than the new job.
3. However, to add this new job we need to create space at the index "i". The second for loop shifts all the elements whose priority is less than the priority of the job to be inserted, one index right so as to create an empty block for the new job ''j" at index "i".
4. Finally, the new job is inserted at the position "i" in the job queue using "q->jobs[i]=j" command.
5. Since a new job is added to the queue now, the variable keeping a count of no of jobs in the queue needs to be incremented which is accomplished through the command "q->njobs++".

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