java - 如何从两个数组列表中删除公共值

Question

我们如何从两个 ArrayList 中删除公共值？

假设我有两个 Arraylist，如下所示：

ArrayList1 = [1,2,3,4]
ArrayList1 = [2,3,4,6,7]

我希望结果为：

ArrayListFinal = [1,6,7]

我该怎么做？

Answer 1

这是您可以遵循的算法来完成任务：

• 构造两个数组的并集
• 构造两个数组的交集
• 从联合中减去交集以获得结果

Java 集合支持addAll、removeAll和retainAll. 用于addAll构造联合、retainAll构造交集和removeAll减法，如下所示：

// Make the two lists
List<Integer> list1 = Arrays.asList(1, 2, 3, 4);
List<Integer> list2 = Arrays.asList(2, 3, 4, 6, 7);
// Prepare a union
List<Integer> union = new ArrayList<Integer>(list1);
union.addAll(list2);
// Prepare an intersection
List<Integer> intersection = new ArrayList<Integer>(list1);
intersection.retainAll(list2);
// Subtract the intersection from the union
union.removeAll(intersection);
// Print the result
for (Integer n : union) {
    System.out.println(n);
}

Answer 2

您实际上是在要求Symmetric Difference。

List<Integer> aList = new ArrayList<>(Arrays.asList(1, 2, 3, 4));
List<Integer> bList = new ArrayList<>(Arrays.asList(2, 3, 4, 6, 7));
// Union is all from both lists.
List<Integer> union = new ArrayList(aList);
union.addAll(bList);
// Intersection is only those in both.
List<Integer> intersection = new ArrayList(aList);
intersection.retainAll(bList);
// Symmetric difference is all except those in both.    
List<Integer> symmetricDifference = new ArrayList(union);
symmetricDifference.removeAll(intersection);

System.out.println("aList: " + aList);
System.out.println("bList: " + bList);
System.out.println("union: " + union);
System.out.println("intersection: " + intersection);
System.out.println("**symmetricDifference: " + symmetricDifference+"**");

印刷：

aList: [1, 2, 3, 4]
bList: [2, 3, 4, 6, 7]
union: [1, 2, 3, 4, 2, 3, 4, 6, 7]
intersection: [2, 3, 4]
**symmetricDifference: [1, 6, 7]**

Answer 3

你可以使用这样的东西：

ArrayList <Integer> first = new ArrayList <Integer> ();
ArrayList <Integer> second = new ArrayList <Integer> ();
ArrayList <Integer> finalResult = new ArrayList <Integer> ();

first.add(1);
first.add(2);
first.add(3);
first.add(4);

second.add(2);
second.add(3);
second.add(4);
second.add(6);
second.add(7);

for (int i = 0; i < first.size(); i++){

    if (!second.contains(first.get(i))){

        finalResult.add(first.get(i));
    }
}


for (int j = 0; j < second.size(); j++){

    if (!first.contains(second.get(j))){

        finalResult.add(second.get(j));
    }

}

正如您在帖子中描述的那样，我刚刚填充了两个 ArrayList，并检查了它们是否有不同的元素；如果找到了这样的元素，我将它们添加到 finalResult ArrayList。

Answer 4

SetList<Integer> A = new SetList<Integer>();
A.addAll({1,2,3,4});

SetList<Integer> B = new SetList<Integer>();
B.addAll({2,3,4,6,7});

Integer a = null;

for (int i=0; i<A.size(); i++)
{
    a = A.get(i);

    if (B.contains(a)
    {
        B.remove(a);
        A.remove(a);
        i--;
    }
}

SetList<Integer> final = new SetList<Integer>();
final.addAll(A);
final.addAll(B);

// final = { 1, 6, 7 }