SDE - 1

You have been given two integers ‘DAY_HOURS’ and ‘PARTS’. Where ‘DAY_HOURS’ is the number of hours in a day and a day can be divided into ‘PARTS’ equal parts. Your task is to find total instances of equivalent prime groups. Prime group refers to the group of elements (hours) which are prime and measure the same equivalent time since the start of the day.

For example, if we consider ‘DAY_HOURS’ to be 24 and ‘PARTS’ to be 2, then the day of total 24 hours is divided into 2 parts ( 1 - 12 ) and ( 13 - 24 ). 5 hours in the first part of the day is equivalent to 17, which is 5 hours into the second part of the day. And since 5 and 17 both are prime, they can be considered as a prime group.

Note:

1. Day starts with hour 1 and ends with hour  ‘DAY_HOURS’.

2. Each hour of the prime group should be in a different part of the day.

3. If there is no prime group then return zero.

4. ‘DAY_HOURS’ should be divisible by ‘PARTS’, meaning that the number of hours per part (DAY_HOURS/PARTS)  should be a natural number.

Example:

Let ‘DAY_HOURS’ = 20  and ‘PARTS’ = 2

Hence the view of our day would be in the following format: 

1  2  3  4  5  6  7  8  9 10      -  Part 1
11 12 13 14 15 16 17 18 19 20     -  Part 2

 1-11  Not a prime group because 1 is not prime.
 2-12  Not a prime group because 12 is not prime.
 3-13  Because both 3 and 13 are prime, it is an equivalent prime group.
 4-14  Not a prime group because 4 and 14 are not prime.
 5-15  Not a prime group because 15 is not prime.
 6-16  Not a prime group, because 6 and 16 are not prime.
 7-17  Because both 7 and 17 are prime, it is an equivalent prime group.
 8-18  Not a prime group, because 8 and 18 are, is not prime.
 9-19  Not a prime group because 9 is not prime.
 10-20 Not a prime group because both 10 and 20 are not prime.

 Hence there are 2 equivalent prime groups in the above format which are 3-13 and 7-17.

You are given two non-negative numbers 'num1' and 'num2' represented in the form of linked lists.

The digits in the linked lists are stored in reverse order, i.e. starting from least significant digit (LSD) to the most significant digit (MSD), and each of their nodes contains a single digit.

Calculate the sum of the two numbers and return the head of the sum list.

Example :

Input:
'num1' : 1 -> 2 -> 3 -> NULL
'num2' : 4 -> 5 -> 6 -> NULL

Output: 5 -> 7 -> 9 -> NULL

Explanation: 'num1' represents the number 321 and 'num2' represents 654. Their sum is 975.