与语言无关的洗牌问题

int countZeroes (int[] vec) {
int ret = 0;
foreach(int i in vec) if (i == 0) ret++;

return ret;
}

int[] mysticCalc(int[] values, int[] indexes) {
    int zeroes = countZeroes(values);
    int[] retval = new int[values.length];
    int product = 1;

    if (zeroes >= 2) { // 2 or more zeroes, all results will be 0
        for (int i = 0; i > values.length; i++) {
            retval[i] = 0;      
        }
        return retval;
    }
    foreach (int i in values) {
        if (i != 0) product *= i; // we have at most 1 zero, dont include in product;
    }
    int indexcounter = 0;
    foreach(int idx in indexes) {
        if (zeroes == 1 && values[idx] != 0) {  // One zero on other index. Our value will be 0
            retval[indexcounter] = 0;
        }
        else if (zeroes == 1) { // One zero on this index. result is product
            retval[indexcounter] = product;
        }
        else { // No zeros. Return product/value at index
            retval[indexcounter] = product / values[idx];
        }
        indexcouter++;
    }  
    return retval;
}

from numpy import array

def product(input, index):
    a = array(input)[index]

    if a[a == 0].size != 1:
        a = a.prod() / a # product except current
    else:
        # exaclty one non-zero-valued element in `a`
        nzi = a.nonzero() # indices of non-zero-valued elements
        a[a == 0] = a[nzi].prod()
        a[nzi] = 0

    return a

for input in ([2,3,4,5], [2,0,4,5], [0,3,0,5]):
    print product(input, [1,3,2,0])

[40 24 30 60]
[40  0  0  0]
[0 0 0 0]

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)

public enum CardValue { A, Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten, J, Q, K }
public enum Suit { Spades, Hearts, Diamonds, Clubs }

public class Card {
    public Card(CardValue value, Suit suit) {
        Value = value;
        Suit = suit;
    }

    public CardValue Value { get; private set; }
    public Suit Suit { get; private set; }
}

public class Deck : IEnumerable<Card> {
    public Deck() {
        initialiseDeck();
        Shuffle();
    }

    private Card[] cards = new Card[52];

    private void initialiseDeck() {
        for (int i = 0; i < 4; ++i) {
            for (int j = 0; j < 13; ++j) {
                cards[i * 13 + j] = new Card((CardValue)j, (Suit)i);
            }
        }
    }

    public void Shuffle() {
        Random random = new Random();

        for (int i = 0; i < 52; ++i) {
            int j = random.Next(51 - i);
            // Swap the cards.
            Card temp = cards[51 - i];
            cards[51 - i] = cards[j];
            cards[j] = temp;
        }
    }

    public IEnumerator<Card> GetEnumerator() {
        foreach (Card c in cards) yield return c;
    }

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() {
        foreach (Card c in cards) yield return c;
    }
}

class Program {
    static void Main(string[] args) {
        foreach (Card c in new Deck()) {
            Console.WriteLine("{0} of {1}", c.Value, c.Suit);
        }

        Console.ReadKey(true);
    }
}

IEnumerable<int> ProductExcept(List<int> l, List<int> indexes) {
    if (l.Count(i => i == 0) == 1) {
        int singleZeroProd = l.Aggregate(1, (x, y) => y != 0 ? x * y : x);
        return from i in indexes select l[i] == 0 ? singleZeroProd : 0;
    } else {
        int prod = l.Aggregate(1, (x, y) => x * y);
        return from i in indexes select prod == 0 ? 0 : prod / l[i];
    }
}

void product_except_current(int input[], int index[], int out[],
                            int len) {
  int prod = 1, nzeros = 0, izero = -1;

  for (int i = 0; i < len; ++i)
    if ((out[i] = input[index[i]]) != 0)
      // compute product of non-zero elements
      prod *= out[i]; // ignore possible overflow problem
    else {
      if (++nzeros == 2)
         // if number of zeros greater than 1 then out[i] = 0 for all i
         break;
      izero = i; // save index of zero-valued element
    }

  //  
  for (int i = 0; i < len; ++i)  
    out[i] = nzeros ? 0 : prod / out[i];                              

  if (nzeros == 1)
    out[izero] = prod; // the only non-zero-valued element
}

#include

class Deck {
  // each card is 8-bit: 4-bit for suit, 4-bit for value
  // suits and values are extracted using bit-magic
  char cards[52];
  public:
  // ...
  void shuffle() {
    std::random_shuffle(cards, cards + 52);
  }
  // ...
};

  // ...
  int main() {
    typedef std::map<std::pair<size_t, Deck::value_type>, size_t> Map;
    Map freqs;    
    Deck d;
    const size_t ntests = 100000;

    // compute frequencies of events: card at position
    for (size_t i = 0; i < ntests; ++i) {
      d.shuffle();
      size_t pos = 0;
      for(Deck::const_iterator j = d.begin(); j != d.end(); ++j, ++pos)
        ++freqs[std::make_pair(pos, *j)];
    }

    // if Deck.shuffle() is correct then all frequencies must be similar
    for (Map::const_iterator j = freqs.begin(); j != freqs.end(); ++j)
      std::cout <<"pos=" << j->first.first <<" card=" << j->first.second
                <<" freq=" << j->second << std::endl;    
  }

    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;
        }
    }