HackerRank Algebra – Tell the Average

Challenge: Tell the Average

Subdomeniu: Algebra (algebra)

Scor cont: 25.0 / 25

Submission status: Accepted

Submission score: 1.0

Submission ID: 464724125

Limbaj: python3

Link challenge: https://www.hackerrank.com/challenges/tell-the-average/problem

Cerinta

James is very naive in Mathematics, He always makes new things out of a given list of integers. Today he is given a list $L$, so he creates a value $S$ out of it.  

$S$ from a given list can be calculated as follows.

    value_of_S(list L)
    {
        while ((number of elements in L) > 1)
        {
            a = L[0]
            b = L[1]
            delete L[1]
            L[0] = a+b+ab
        }
        return L[0] % 1000000007
    }
    
James has an ample amount of time, so he calculates the values of $S$ for all the permutations of the given list $L$ and finds their average value. Then he asks you to report that value.
 
**Input Format**  
The first line contains an integer $N$, the number of integers in the list.  
The second line contains $N$ integral values, $L[0], \ldots, L[N-1]$, separated by single spaces.

**Output Format**  
Print the [floor](http://en.wikipedia.org/wiki/Floor_and_ceiling_functions) of the average value.

**Constraints**  
$2 \le N \le 10^4$  
$2 \le L[i] \le 10^6$

**Sample Input**  

    2
    2 3

**Sample Output**  

    11

**Explanation**  
The $S$ value corresponding to the two permutations of the given list is $11$.

Cod sursa

from functools import reduce

MOD = 1_000_000_007

def _value_of_S_reduce(x:int,y:int)->int:
    return (x+y+x*y) % MOD

def value_of_S(l:list)->int:
    return reduce(_value_of_S_reduce,l)
    
if __name__=='__main__':
    _ = input()
    print(value_of_S(list(map(int,input().split()))))