Hi, I have written the code and two test cases are passing, but one test case is not passing, it showing TLE. Can anyone please tell me the optimized solution and where am I doing wrong.
Two test cases are passing and one test case is showing TLE
Precompute the prime numbers using sieve technique.
In the sieve technique where you create a boolean array of 1000005 size.
And start from the first prime number i.e. 2. Take its square(4) and increment it by the number you took (i.e. 4,6,8,10 and so on). Mark all these as false since they cannot be primes.
Now take the next unmarked number, 3. And mark 9,12,15 and so as false. Similarly do it for 4. 16,20,24 and so on as false.
When you finish the loop, count the number of primes within the range.
Further explained:
In the image below, say we have to get all primes between 1-100. First outside the loop mark 1 as not a prime number (in case of boolean array as true or in int array as 1).
Now enter a for loop:
find the index which has set value as 0. initially it will be 2.
Start another for loop and mark all the numbers which are divisible by 2 and are greater than or equal to the square of it as true/1 (not primes). these numbers will be 4,6,8,10 and so on.
Now the next number will be 3. these numbers will be 9,12,15 and so on.
Similarly do it till 10 if total numbers are 100.
After this do a simple traversal to store all the prime numbers. Refer to the image below for a visualization
you can see this video to understand the basic logic
https://www.youtube.com/watch?v=8sniiDbfPK4
Day 6 - Prime Visits | Pre-computing Primes using Sieve | Competitive…
if it solves your doubt, please mark it as resolved
Hey, Thanks for the explanation. Do these types of questions come in interviews? I mean this question is of competitive programming type. All the questions which are in assignments are mandatory to do for interviews or some of those are for competitive programming.
see this is a very basic question if the time constraints were a little lose.so there can be a q like this in the interview asking u to better your basic approach .you can use this there