shuffle card deck issues in language agnostic [closed]

Answer 1

In Haskell:

import Array

problem1 input index = [(left!i) * (right!(i+1)) | i <- index]
  where left  = scanWith scanl
        right = scanWith scanr
        scanWith scan = listArray (0, length input) (scan (*) 1 input)

Answer 2

Trilsson made a separate topic about the testing part of the question

How to test randomness (case in point - Shuffling)

very good idea Trilsson:)

Answer 3

Second problem.

    public static void shuffle (int[] array) 
    {
        Random rng = new Random();   // i.e., java.util.Random.
        int n = array.length;        // The number of items left to shuffle (loop invariant).
        while (n > 1) 
        {
            int k = rng.nextInt(n);  // 0 <= k < n.
            n--;                     // n is now the last pertinent index;
            int temp = array[n];     // swap array[n] with array[k] (does nothing if k == n).
            array[n] = array[k];
            array[k] = temp;
        }
    }

This is a copy/paste from the wikipedia article about the Fisher-Yates shuffle. O(n) complexity