Hey Guys, there was a question in Round 2 of the HackWithInfy Contest which I feel is quite nice and I wasn't able to think of any possible solution to it. So the question goes like that:-

We have defined a function f(x) = sum of all the digits of x. Now,

0 <= i <= N

0 <= j <= N

We have to count how many pairs are there which satisfy the condition that f(i) + f(j) is a prime.

Constraints:- 0 <= N <= 10^50

Example:-

1) N = 2

pairs = 2

2) N = 3

pairs = 4

Can anyone suggest some possible method to solve this question??

Hey Guys!! I have been trying to understand the Editorial's solution from quite a while now but couldn't get it properly. Can anyone please throw some light on how to proceed it.

Question link :- https://codeforces.net/contest/1163/problem/D

What I have understood till now.

At every position, we will assume every possible character to be there in the string c whenever there is asterisk present and after that, we are also maintaining what is the length of the prefix of string t and s which matches with the suffix of string c[0, i]. Now, how to move beyond this?

Additional help :-

Can someone provide some similar questions to this one which they have encountered while practicing.

Hey Guys, My solution to the third problem of yesterday's round(Educational Round 63) fails on test case 20 according to Codeforces compiler but I am getting the correct answer on my own compiler and even on dry running it by myself.

Question link :-https://codeforces.net/contest/1155/problem/C

Solution link :-https://codeforces.net/contest/1155/submission/53144801

Test case on which it is failing :

2 1 10000000000 20000000000 10000000000

Plzz Guys see to it what's happening here !!

Hey Guys!! Can anyone give some insights on how to approach this problem from Yesterday's contest?

Problem link : http://codeforces.net/contest/705/problem/C

Solution link :- http://codeforces.net/contest/705/submission/42254642

Hey guys this code is giving me the runtime error in testcase-2 on submitting it while on running the same test on my system it is giving me correct answer. I literally have no clue of what's happening :(

Could anyone plzz help me out!!