[Toy]SuffleDeck.js

SuffleDeck

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덱을 랜덤하게 suffle하는 문제입니다. 전에 비슷한 문제를 푼적이 있어 그런식으로 해보았네요.

/**

• Given an array containing a deck of cards, implement a function that shuffles
• the deck.
  *
• Example:
• var deck = orderedDeck();
• // [“A♥”,”2♥”,”3♥”,…,”J♦”,”Q♦”,”K♦”]
• shuffleDeck(deck);
• // [“2♠”,”J♣”,”A♦”, … ,”7♣”,”8♣”,”K♠”]
  *
• Note:
• A shuffled deck should be completely random. That means that a given card should
• be as likely as any other to appear in a given deck index, completely independent
• of the order of the input deck. Think carefully about how to be sure your algorithm
• generates a properly shuffled deck— it is easy to accidentally create a biased algorithm.
  *
• Extra credit:
• • Even a naive algorithm can easily run in linear time. However, does your
• algorithm remain unbiased as N (the deck size) increases? How do you know?
• • Once you have created a properly random, linear algorithm, what is its space complexity?
• There is an algorithm that uses O(N) time and O(1) space (i.e., an in-place shuffle).
  *
• A further note on randomness:
• Technically, a computer-shuffled deck will usually be “pseudorandom”,
• not “truly” random. However, the difference between the two is too small to
• be detectable by any known test.
• See http://en.wikipedia.org/wiki/Pseudorandom_number_generator .
  *
• A human shuffler is much more biased; it takes around seven normal “riffle”
• shuffles before a real deck is actually randomized.
• See https://www.dartmouth.edu/~chance/teaching_aids/books_articles/Mann.pdf .
  */

---

var shuffleDeck = function(deck) {
  // Your code here
};

// Ordered deck generator provided for your testing convenience
// (You may alter this function, but an unaltered copy will be used for tests.)
var orderedDeck = function() {
  var suits = [ '♥', '♣', '♠', '♦' ];
  var values = [ 'A', 2, 3, 4, 5, 6, 7, 8, 9, 10, 'J', 'Q', 'K' ];
  var deck = [];

  suits.forEach(function(suit) {
    values.forEach(function(value) {
      deck.push(value + suit);
    });
  });

  return deck;
};

---

Answer!

---

var shuffleDeck = function(deck) {
  for ( let i = 0; i < deck.length; i++ ) {
    let num = Math.floor( Math.random() * ( deck.length - 1 ) );
    let temp =  deck[i];
    deck[i] = deck[num];
    deck[num] = temp;
  }
  return deck;
};

더 좋은 코드 있으시면 공유해주시면 공유해주세요!