Activity Selection Problem in DSA C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main goal of the Activity Selection Problem?

To select the maximum number of activities that don't overlap in time from a given set of activities.

beginner

Which greedy choice is used in the Activity Selection Problem?

Always pick the activity that finishes earliest among the remaining activities.

beginner

Why do we sort activities by their finish time in the Activity Selection Problem?

Sorting by finish time helps to easily pick the next activity that finishes earliest and does not overlap with previously selected activities.

intermediate

What is the time complexity of the Activity Selection Problem solution using the greedy approach?

O(n log n) due to sorting the activities by their finish time. The selection process itself is O(n).

intermediate

In the Activity Selection Problem, what happens if two activities have the same finish time?

You can choose either one since both finish at the same time; the greedy approach still works correctly.

What is the first step in solving the Activity Selection Problem?

A Sort activities by their finish time

B Sort activities by their start time

C Select the longest activity first

D Select activities randomly

Sorting activities by their finish time allows the greedy algorithm to pick the earliest finishing activity first.

After selecting an activity, what is the next step?

A Select the next activity that starts after the current activity finishes

B Select the next activity that starts before the current activity finishes

C Select the activity with the longest duration

D Select the activity with the earliest start time

We pick the next activity that starts after the current one finishes to avoid overlap.

What type of algorithm is used to solve the Activity Selection Problem efficiently?

A Backtracking

B Dynamic programming

C Divide and conquer

D Greedy algorithm

The greedy algorithm works because choosing the earliest finishing activity leads to an optimal solution.

If activities are not sorted, what is the impact on the solution?

A The solution will be optimal anyway

B The solution will run faster

C The solution may not be optimal

D Sorting is not needed

Without sorting by finish time, the greedy choice may fail and the solution may not be optimal.

What is the output of the Activity Selection Problem?

A All activities sorted by duration

B Maximum set of non-overlapping activities

C All activities sorted by start time

D Minimum set of overlapping activities

The goal is to select the largest number of activities that do not overlap.

Explain the greedy strategy used in the Activity Selection Problem and why it guarantees an optimal solution.

Think about how picking the earliest finishing activity leaves room for more activities.

Describe the steps to implement the Activity Selection Problem solution in C.

Start with sorting, then pick activities one by one checking start and finish times.