Can anybody please explain me this question in detail and why they use binary search ?

Question : Find minimum time to finish all jobs with given constraints - GeeksforGeeks

If you want to know how to solve such problems using binary search, watch this video : Discrete Binary Search | In-depth with example problem - YouTube

I watched the video and understand the concept of discrete binary search but i am not able to relate with this problem. Can you please help me.

Please help me to solve my doubt.

If you want to solve this problem without binary search then u will have to check all possibility. To be more precise, suppose you can do all job in 1 day(best case) and in the worst case it takes n days, n can be very large like 2e5; So If you check linearly from day 1 to n it will take O(n^2) = O(n) for linear check and an inner loop which will also run for n times to check the answer is correct or not.

But you can optimize the code by binary search as log2(2e5) is only 17. Here your code is running 17 * O(n) for check possible or not which is almost O(n). And you know the difference between O(n^2) vs O(n).