“This is the 19th day of my participation in the Gwen Challenge in November. Check out the details: The Last Gwen Challenge in 2021”

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Java with Notes: Java with Notes

  • Recently, leetCood has become obsessed with writing a card shuffle implementation.

  • The first impression in your brain is made with random numbers:

    • Random numbers range from 1 to 54
    • Create a set to store randomly generated numbers
    • New random numbers are discarded if they exist in the set, and added otherwise.

  • Take a look at the code:

    • Public static void ShuffleTheDeck() {system.out.println (" start time: " + new Date()); List reslutList = new ArrayList(); // start Random shuffle Random = new Random(); while (true) { int endRand = random.nextInt(54); reslutList.add(endRand+1); if (ifRepeat(reslutList) == false) { reslutList.remove(reslutList.size() - 1); } if (reslutList.size() >= 54) { break; }} system.out.println (" end time: "+ new Date()); for (int j = 0; j < reslutList.size(); j++) { System.out.println(reslutList.get(j).toString()); Public static Boolean ifRepeat(List List) {HashSet set = new public static Boolean ifRepeat(List List) {HashSet set = new HashSet<>(list); Boolean bool = set.size() == list.size() ? true : false; return bool; }Copy the code
    • Execution Result:
    • Barely?

  • But what are our actual cards?

    • 1-10 J Q K King Xiao Wang
    • A total of 15
    • In addition to the big wang single, the others are four, and respectively, hearts, spades, diamonds, clubs.
    • How do you optimize it?

  • Let’s add an entity class here to store the cards that are generated each time.

  • class poker { public poker(String color, String num) { super(); this.color = color; this.num = num; } String color; String num; public String toString() { return color+num; }}Copy the code

  • Let’s write generate first, and then shuffle.

  • The difference is defining the suit and the face.

  • Public static void buildPoker(){String[] colors = {" spades "," diamonds "," clubs "," hearts "}; String[] nums = {"A","2","3","4","5","6","7","8","9","10","J","Q","K"}; LinkedList pokers = new LinkedList(); for(int i=0; i < colors.length; i++) { for(int j=0; j<nums.length; j++) { pokers.add(new poker(colors[i],nums[j])); }} pokers.add(new poker(" xiao Wang "," black ")); Pokers. Add (new poker(" King "," red ")); }Copy the code

  • Now that the whole deck is generated, here’s how to shuffle it randomly.

  • Shuffle: or use random number to control!

  • Public static void buildPoker(){String[] colors = {" spades "," diamonds "," clubs "," hearts "}; String[] nums = {"A","2","3","4","5","6","7","8","9","10","J","Q","K"}; LinkedList pokers = new LinkedList(); for(int i=0; i < colors.length; i++) { for(int j=0; j<nums.length; j++) { pokers.add(new poker(colors[i],nums[j])); }} pokers.add(new poker(" xiao Wang "," black ")); Pokers. Add (new poker(" King "," red ")); // shuffledpokers = new LinkedList(); while(shuffledpokers.size()<pokers.size()) { Random x = new Random(); poker poke = (poker) pokers.get(x.nextInt(pokers.size())); if(! shuffledpokers.contains(poke)) { shuffledpokers.add(poke); }} system.out. println(" before: "+pokers); System.out.println(" +shuffledpokers); }Copy the code

  • Execution Result:

  • Can do shuffle!
  • Individual think, although very get, but also calculate a train of thought.
  • Please point out any mistakes.

The road ahead is long, I see no end, I will search high and low

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