README
Sum by Factors
Given an array of positive or negative integers
I= [i1,..,in]
you have to produce a sorted array P of the form
[ [p, sum of all ij of I for which p is a prime factor (p positive) of ij] ...]
P will be sorted by increasing order of the prime numbers. The final result has to be given as a string in Java, C#, C, C++ and as an array of arrays in other languages.
Example:
I = [12, 15] # result = [[2, 12], [3, 27], [5, 15]]
[2, 3, 5] is the list of all prime factors of the elements of I,
hence the result.
Notes:
It can happen that a sum is 0 if some numbers are negative!
Example: I = [15, 30, -45] 5 divides 15, 30 and (-45) so 5 appears
in the result, the sum of the numbers for which 5 is a factor is 0 so
we have [5, 0] in the result amongst others.
In Fortran - as in any other language - the returned string is not permitted to contain any redundant trailing whitespace: you can use dynamically allocated character strings.