How to compute sum of all the combinations of given list of numbers? -


suppose have list of numbers - a1,a2,a3,a4,a5,....,an.

how can compute - (a1*a2)+(a1*a3)+(a1*a4)+(a1*a5)+(a1*a6)+....?

ex-for 1,2,3 ,i need calculate 1*2+2*3+1*3=11.

also generalize solution combinations containing more 2 terms ex 3 terms-(a1*a2*a3)+(a1*a3*a4)+(a1*a4*a5)+(a2*a3*a4)+....

import itertools def sumofcombinations(l,s):     return sum(prod(seq) seq in (itertools.combinations(l, s)))  def prod(l):     product = 1     x in l:         product*=x     return product  #exemple mylist = [1,2,3] size = 2 print(sumofcombinations(mylist,size))

this job in python. there more pythonic ways accomplish this. results there.


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