一个数组的所有可能的组合 [英] All possible combinations of an array

问题描述

我有一个字符串数组

{"ted", "williams", "golden", "voice", "radio"}

和我想在下面的表格这些关键字的所有可能的组合：

and I want all possible combinations of these keywords in the following form:

{"ted",
 "williams",
 "golden", 
 "voice", 
 "radio",
 "ted williams", 
 "ted golden", 
 "ted voice", 
 "ted radio", 
 "williams golden",
 "williams voice", 
 "williams radio", 
 "golden voice", 
 "golden radio", 
 "voice radio",
 "ted williams golden", 
 "ted williams voice", 
 "ted williams radio", 
 .... }

我已经准备了几个小时，没有有效的结果（高级编程??副作用）。

I've been going for hours with no effective result (side effect of high-level programming ??).

我知道解决的办法应该是显而易见的，但我坚持，说实话！用Java / C＃解决方案被接受。

I know the solution should be obvious but I'm stuck, honestly ! Solutions in Java/C# are accepted.

修改

1. 这不是一个功课
2. 在特德·威廉斯和泰德·威廉姆斯被认为是相同的，所以我想特德·威廉斯只有

编辑2 ：审查答案的链接后，事实证明，番石榴用户可以在com.google.common.collect.Sets的幂方法

EDIT 2: after reviewing the link in the answer, it turns out that Guava users can have the powerset method in com.google.common.collect.Sets

推荐答案

编辑：作为FearUs指出，一个更好的解决方案是使用番石榴的<一个href="http://docs.guava-libraries.google$c$c.com/git/javadoc/com/google/common/collect/Sets.html#powerSet(java.util.Set)"相对=nofollow> Sets.powerset（设置设置）。你可以看到code（约）<一href="https://$c$c.google.com/p/guava-libraries/source/browse/guava/src/com/google/common/collect/Sets.java#1276"相对=nofollow>这里。

As FearUs pointed out, a better solution is to use Guava's Sets.powerset(Set set). You can see the code (around) here.

该解决方案：

public static void main(String[] args) {

    List<List<String>> powerSet = new LinkedList<List<String>>();

    for (int i = 1; i <= args.length; i++)
        powerSet.addAll(combination(Arrays.asList(args), i));

    System.out.println(powerSet);
}

public static <T> List<List<T>> combination(List<T> values, int size) {

    if (0 == size) {
        return Collections.singletonList(Collections.<T> emptyList());
    }

    if (values.isEmpty()) {
        return Collections.emptyList();
    }

    List<List<T>> combination = new LinkedList<List<T>>();

    T actual = values.iterator().next();

    List<T> subSet = new LinkedList<T>(values);
    subSet.remove(actual);

    List<List<T>> subSetCombination = combination(subSet, size - 1);

    for (List<T> set : subSetCombination) {
        List<T> newSet = new LinkedList<T>(set);
        newSet.add(0, actual);
        combination.add(newSet);
    }

    combination.addAll(combination(subSet, size));

    return combination;
}

测试：

$ java PowerSet ted williams golden
[[ted], [williams], [golden], [ted, williams], [ted, golden], [williams, golden], [ted, williams, golden]]
$

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