使用功能接口的功能集

Question

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想要改进此问题吗？添加详细信息，并通过

闭合 2年前。

Answer 1

尝试一下。

public static <T> Set<Function<T, T>> bijectionsOf(Set<T> set) {
    ArrayList<T> domain = new ArrayList<>(set);
    return permutations(domain, new ArrayList<>(), set.size(), 0)
        .stream()
        .map(list -> (Function<T, T>) t -> list.get(domain.indexOf(t)))
        .collect(Collectors.toSet());
}

输出：

1 --> 1; 2 --> 3; 3 --> 2;
1 --> 3; 2 --> 2; 3 --> 1;
1 --> 2; 2 --> 1; 3 --> 3;
1 --> 3; 2 --> 1; 3 --> 2;
1 --> 1; 2 --> 2; 3 --> 3;
1 --> 2; 2 --> 3; 3 --> 1;