CSC 345 Section 8.11
On average, how many comparisons does Quicksort require to sort 1000 records (to the nearest 1000 comparisons)?
10000
In which cases are the time complexities the same for Quicksort? Worst and Best only Worst, Average, and Best Best and Average only Worst and Average only
Best and Average only
When is Quicksort a good choice for sorting an array? The processor speed is fast Each record requires a large amount of memory In most standard situations where you want to sort many records None of the above
In most standard situations where you want to sort many records
When selecting a pivot value, a simple thing to do is to always pick from the same place in the partition. If we use this approach, does it matter whether we always pick from the first position in the partition, the last position in the partition, or the middle position in the partition? It doesn't really matter, they are all equally good or bad It is much better to pick the first value It is much better to pick the middle value It is much better to pick the last value
It is much better to pick the middle value
If it takes a given computer one second on average to run Quicksort on an array of 1000 records, how long (to the nearest thousand seconds) will it take to run Quicksort on 1,000,000 records? (Hint: You know from this statement that the machine can do about 10,000 comparisons per second. To get the answer, you first need to compute about how many total comparisons 1,000,000 records will require.)
2000
The order of the input records has what impact on the number of comparisons required by Quicksort (as presented in this module)? None There is a big difference, the asymptotic running time can change There is a constant factor difference
There is a big difference, the asymptotic running time can change
(For the version of the algorithm as presented in this module:) What is the running time of Quicksort when the input is an array where all record values are equal? Θ(n) Θ(n^n) Θ(n^2) Θ(logn) Θ(nlogn)
Θ(n^2)
What is the average-case cost for Quicksort to sort an array of n elements? Θ(n^2) Θ(nlogn) Θ(n) Θ(logn)
Θ(nlogn)
What is the best-case cost for Quicksort to sort an array of n elements? Θ(n^2) Θ(nlogn) Θ(n) Θ(logn)
Θ(nlogn)
What is the worst-case cost for Quicksort to sort an array of n elements? Θ(n^2) Θ(nlogn) Θ(n) Θ(logn)
Θ(n^2)
A disadvantage of Quicksort is: It is stable Its worst-case running time is Θ(n^2) Its average-case running time is Θ(n^2) It needs an extra array for auxilliary storage
Its worst-case running time is Θ(n^2)
Quicksort (as the code is written in this module) is a stable sorting algorithm. Recall that a stable sorting algorithm maintains the relative order of records with equal keys. True False
False
After Quicksort completes the partition function, where is the pivot? Between the smaller values and the greater values in the partition The last position in the partition The first position in the partition The middle position in the partition
The last position in the partition
What is the worst-case cost for Quicksort's partition step? Θ(n^2) Θ(nlogn) Θ(n) Θ(logn)
Θ(n)