Can any one share any simple approach for the problem chef and prime queries in in the June challenge asked 12 Jun '17, 15:39

This question took a long while and a lot of WA/TLE to solve. Here's my approach without using trees:
Here is the link to my solution: https://www.codechef.com/viewsolution/14155947 answered 12 Jun '17, 15:51
you would have used functions in your solution instead of doing everything in the main() function so that it will be bit easier to understand
(12 Jun '17, 16:01)
I'm sorry, I had not planned to be sharing the code so didn't bother making it more readable. I was just desperately trying to get an AC.
(12 Jun '17, 16:05)
I have used the same approach, you can see my code for reference here.
(12 Jun '17, 16:59)
Is this approach similar to(In general) maintaining a cumulative frequency of primes then binary searching the indices for x and y ? and doing this thing with either Segment tree/square root decomposition ?
(12 Jun '17, 17:05)

Mine solution is a simple one. Just use the sqrt trick for summation between ranges. As in this problem, along with ranges, another query pair (X, Y) is added, maintain prefix sum for it over the sqrtroot ranges. 2 things are needed to be taken care of in this method:
Here is a link to my solution Extra : This method can also handle point  updates as well and it completely online solution. Complexity : $O(P \sqrt(N) + Q*sqrt(P))$, where $P$ is same as above answered 12 Jun '17, 16:56

Hey, This problem can be solved using just segment tree, The approach is we can store the prime factors as key and their count as the value in the leaf nodes of segment tree and we can merge the same keys and add up their count. I have written a blog which explains my solution, have a look here. Link to the blog. answered 12 Jun '17, 17:39

We can also view this problem as finding the number of points inside a rectangle. The points are of the form (X,Y) where X is the index of the number arr[X] in the array and for each X, Y's are the Prime factors of arr[X]. The queries are of the form L,R,X,Y which translate to the rectangle formed by x=L,x=R,y=X,y=Y. So we have points in 2d plane and queries are given by rectangles. we have to find the number of points inside this rectangle(including the border) which can be done by segment trees, Square root decomposition etc. answered 13 Jun '17, 13:02

You can use a Persistent Segment Tree to store the sum of exponents of Primes. And then for every array element upgrade the Tree with the new sum of exponents. Your answer would be query(version[r])query(version[l1]), taking version[0] to be completely empty. answered 12 Jun '17, 15:48

I generated all prime numbers till 10^6. I took each prime number and found out how many of its multiples exist in the array. in the given example 2 3 4 5 is the array and first prime number is 2 so at each of the indices that contains a multiple of 2 add the exponent(to an empty array initially) given array:2 3 4 5 initially: 0 0 0 0 state 0 for 2 the array becomes : 1 0 2 0 state 1 then for 3: 1 1 2 0state 2 for 5: 1 1 2 1state 3 each of these is a state so for l,r,x,y such as 1 3 2 3 the answer is sum of numbers from 1 to 3 in state 2 minus that in state 0. I was stuck here then I saw Gaurav sen's video on persistent segment trees and got the answer in the required time. answered 12 Jun '17, 15:51

My solution is an offline solution. First prime factorise all the numbers of the array and store it in a vector. For each index of the array find the starting point of the value in the vector. Now for a (L,R,X,Y) query we can treat it as number of elements in (L,R)>X  number of elements in(L,R)>Y. With this information we can do offline preprocessing and solve it using a normal segment tree. For offline preprocessing we sort all queries and the elements of the segment tree and solve it . See my solution for more details. answered 12 Jun '17, 16:04

Is there any way to get rid off TLE from my solution solution please help me out! answered 12 Jun '17, 16:47
@vivek4434 , it will be useful for the code reviewer if you can provide some comments to explain what you are doing and if possible, use functions
(12 Jun '17, 19:08)
Tell me where you find difficulty to understand code?
(12 Jun '17, 20:39)

Hey, you can use Merge Sort segment tree. answered 12 Jun '17, 17:46

what we actually store in each node if we use persistent segment trees answered 12 Jun '17, 18:23

@vivek_reddy can u please explain your approach & code for triplets?
just try to find number of times each unique product term repeats and you need to modular arithmetic
Hey, This problem can be solved using segment tree, I have written a thorough blog on how to solve this problem using segment tree, please visit it here https://codelikepros.blogspot.in/2017/06/solvingcodechefjunelongchallenge.html
awesome !!