FizzBuzz 号码分组

Question

我正尝试在 Java8 中编写 FizzBuzz 问题。它工作正常，我得到了想要的输出。对于能被“3”整除的数，应该return"Fizz"，对于能被“5”整除的数，应该return"Buzz"，对于能被两者整除的数, 它应该 return "FizzBuzz".

如果我将值作为“15”传递，它 returns:

["1","2","Fizz","4","Buzz","Fizz","7","8","Fizz","Buzz","11","Fizz","13","14","FizzBuzz"]

现在，我被困在一件事上。如果我将值作为“15”传递，我想获得如下输出：

{"Fizz": [3, 6, 9, 12],"Buzz": [5, 10],"FizzBuzz": [15]}

我想按 Fizz、Buzz 和 FizzBuzz 对数字进行分组。

这是我的代码：

public class FizzBuzzService {

private Map<Rule, String> ruleContainers = new HashMap();
private Set<Rule> rules  = new HashSet();

public FizzBuzzService(){
    addRule(i -> i % 15 == 0, "FizzBuzz");
    addRule(i -> i % 3 == 0, "Fizz");
    addRule(i -> i % 5 == 0, "Buzz");
}

public void addRule(Rule rule, String res) {
    rules.add(rule);
    ruleContainers.put(rule, res);
}

public String getValue(int i) {
    for (Rule rule : rules) {
        if (rule.apply(i)) {
            return ruleContainers.get(rule);
        }
    }
    return String.valueOf(i);
}

//then the origin code should be as follows:
public List<String> fizzBuzz(int n) {
     List<String> res = new ArrayList();
     for(int i = 1; i <= n; i++){
         res.add(getValue(i));
     }
     return res;
 }

interface Rule{
    boolean apply(int i);
}
}

如果有人能指导我，我将不胜感激。谢谢

Answer 1

我会 return Map<String, List<Integer>>（使用 LinkedHashMap 而不是 HashMap 并且您的密钥将保留插入顺序）创建 List<Integer>(s ) 对于 fizz、buzz 和 fizzbuzz 值。它可以用一个 static 方法完成，例如

public static Map<String, List<Integer>> fizzBuzz(int n) {
    Map<String, List<Integer>> map = new HashMap<>();
    List<Integer> fizz = new ArrayList<>(), //
            buzz = new ArrayList<>(), //
            fizzbuzz = new ArrayList<>();
    IntStream.rangeClosed(1, n).forEachOrdered(i -> {
        boolean f = i % 3 == 0, b = i % 5 == 0;
        if (f && b) {
            fizzbuzz.add(i);
        } else if (f) {
            fizz.add(i);
        } else if (b) {
            buzz.add(i);
        }
    });
    map.put("Fizz", fizz);
    map.put("Buzz", buzz);
    map.put("FizzBuzz", fizzbuzz);
    return map;
}

Answer 2

Map<String, List<Integer>> map = 
  IntStream.rangeClosed(1, 15)
    .mapToObj(n -> {
        String str = n % 15 == 0 ? "FizzBuzz" : 
            (n % 5 == 0) ? "Buzz" : (n % 3 == 0) ? "Fizz" : null;
        return str == null ? null : new SimpleEntry<>(str, n);
    }).filter(Objects::nonNull)
    .collect(groupingBy(Entry::getKey, mapping(Entry::getValue, toList())));

System.out.println(map);

Answer 3

这里有一种使用流的方法：

Map<String, List<String>> result = IntStream.rangeClosed(1, n)
    .filter(i -> i % 3 == 0 || i % 5 == 0)
    .boxed()
    .collect(Collectors.groupingBy(i ->
        i % 15 == 0 ? "FizzBuzz" :
        i %  3 == 0 ? "Fizz" : 
                      "Buzz"));

没有流：

Map<String, List<String>> result = new HashMap<>();
for (int i = 0; i < n; i++) {
    if (i % 3 == 0 || i % 5 == 0) {
        String key = i % 15 == 0 ? "FizzBuzz" :
                     i %  3 == 0 ? "Fizz" : 
                                   "Buzz";
        result.computeIfAbsent(key, k -> new ArrayList<>()).add(i);
    }
}

Answer 4

第 1 步：对号码应用规则。

步骤 2： 找到第一个匹配规则。

第三步：过滤不符合任何规则的元素。

第 4 步： 按规则关键字分组

    public static void main(String[] args) {

        FizzBuzzService();
         Map<String, List<Integer>> fizzBuzzMap = IntStream.range(1, 31)
                  .mapToObj(number->applRule(number))
                  .filter(obj ->obj!=null)
                  .collect(Collectors.groupingBy(Entry::getKey,Collectors.mapping(Entry::getValue, Collectors.toList())));

         System.out.println("FizzBuzzMap : " + fizzBuzzMap);
    }

    private static SimpleEntry<String, Integer> applRule(Integer number) {

        Optional<Entry<Rule, String>> findFirst = ruleContainers.entrySet()
                                                                .stream()
                                                                .filter(rule -> rule.getKey().apply(number))
                                                                .findFirst();
        if (findFirst.isPresent()) {
            System.out.println("Number : " + number + " First Matching Rule : " +findFirst.get().getValue());
            return new SimpleEntry<>(findFirst.get().getValue(), number);
        }

        return null;
    }
}

    public static void FizzBuzzService(){
        addRule(i -> i % 3 == 0, "Fizz");
        addRule(i -> i % 5 == 0, "Buzz");
        addRule(i -> i % 15 == 0, "FizzBuzz");
    }

输出：

Number : 3 First Matching Rule : Fizz
Number : 5 First Matching Rule : Buzz
Number : 6 First Matching Rule : Fizz
Number : 9 First Matching Rule : Fizz
Number : 10 First Matching Rule : Buzz
Number : 12 First Matching Rule : Fizz
Number : 15 First Matching Rule : FizzBuzz
Number : 18 First Matching Rule : Fizz
Number : 20 First Matching Rule : Buzz
Number : 21 First Matching Rule : Fizz
Number : 24 First Matching Rule : Fizz
Number : 25 First Matching Rule : Buzz
Number : 27 First Matching Rule : Fizz
Number : 30 First Matching Rule : FizzBuzz
FizzBuzzMap : {FizzBuzz=[15, 30], Fizz=[3, 6, 9, 12, 18, 21, 24, 27], Buzz=[5, 10, 20, 25]}

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