我正在尝试生成 List<List<String>>
的所有排列但我没有得到独特的排列。
我的List<List<String>>
看起来像
[
[Test, Test 1, Test 2],
[Apple, Sandwich, Banana],
[Cake, Ice Cream, Fruit]
]
我正在尝试为每个 List<String
获取所有可能的组合在父级内List<String>
。因此,例如,第一个实例应该具有:
[Test, Test 1, Test 2]
[Test, Test 2, Test 1]
[Test 2, Test, Test 1]
[Test 2, Test 1, Test]
[Test 1, Test, Test 2]
[Test 1, Test 2, Test]
现在,我的尝试只是迭代并重复元素而不改变顺序,所以 [Test, Test 1, Test 2]
只会重复父项 List<String>
的大小。这是我的方法。感谢任何帮助:
List<List<String>> allPerms = parentList.stream().map(line -> parentList.stream()).flatMap(l -> l.filter(j -> !j.equals(l))).collect(Collectors.toList());
最佳答案
使用CollectionUtils.permutations
public static void showAllPermuteByCommons(List<String> list) {
CollectionUtils.permutations(list) //
.stream() //
.forEach(System.out::println);
}
或者原路返回
public static void permute(List<String> list, int left, int right) {
if (left == right) {
System.out.println(Arrays.toString(list.toArray()));
return;
}
for (int j = left; j <= right; j++) {
Collections.swap(list, left, j);
permute(list, left + 1, right);
Collections.swap(list, left, j);
}
}
public static void showAllPermute(List<String> list) {
int size = list.size();
permute(list, 0, size - 1);
}
测试
List<List<String>> list = new ArrayList<>();
list.add(Arrays.asList("Test", "Test 1", "Test 2"));
list.add(Arrays.asList("Apple", "Sandwich", "Banana"));
list.add(Arrays.asList("Cake", "Ice Cream", "Fruit"));
// list.forEach(t -> showAllPermuteByCommons(t));
list.forEach(t -> showAllPermute(t));
输出
[Test, Test 1, Test 2]
[Test, Test 2, Test 1]
[Test 2, Test, Test 1]
[Test 2, Test 1, Test]
[Test 1, Test 2, Test]
[Test 1, Test, Test 2]
[Apple, Sandwich, Banana]
[Apple, Banana, Sandwich]
[Banana, Apple, Sandwich]
[Banana, Sandwich, Apple]
[Sandwich, Banana, Apple]
[Sandwich, Apple, Banana]
[Cake, Ice Cream, Fruit]
[Cake, Fruit, Ice Cream]
[Fruit, Cake, Ice Cream]
[Fruit, Ice Cream, Cake]
[Ice Cream, Fruit, Cake]
[Ice Cream, Cake, Fruit]
关于java - 如何生成 List<List<String>> 的所有排列?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58314196/