Activity selection problem

#1

https://online.codingblocks.com/app/player/69195/content/115367/5280/code-challenge

please explain this problem.

#2

Explanation

Example 1 :
3
10 20
12 15
20 30

Consider the above 3 activities sorted by
by finish time.
start[] = {10, 12, 20};
finish[] = {20, 25, 30};
A person can perform at most two activities. The
maximum set of activities that can be executed
is {0, 2} [ These are indexes in start[] and
finish[] ]

Example 2 :
6
1 2
3 4
0 6
5 7
8 9
5 9
Consider the above 6 activities
sorted by by finish time.
start[] = {1, 3, 0, 5, 8, 5};
finish[] = {2, 4, 6, 7, 9, 9};
A person can perform at most four activities. The
maximum set of activities that can be executed
is {0, 1, 3, 4} [ These are indexes in start[] and
finish[] ]

Approach

idea is to use Greedy Algorithm

The greedy choice is to always pick the next activity whose finish time is least among the remaining activities and the start time is more than or equal to the finish time of previously selected activity. We can sort the activities according to their finishing time so that we always consider the next activity as minimum finishing time activity.

Algorithm

  1. Sort the activities according to their finishing time
  2. Select the first activity from the sorted array and print it.
  3. Do following for remaining activities in the sorted array.
    …….a) If the start time of this activity is greater than or equal to the finish time of previously selected activity then select this activity and print it.

i hope this helps
if yes hit a like and don’t forgot to mark doubt as resolved :grinning:
if you have more doubts regarding this feel free to ask