如何使用另一个数组列表提供的索引比较数组列表中的元素

Question

I have an ArrayList: A containing array of indexes something like this [[0,1],[4,5,6]] . This list is dynamic and may grow in size based on some prior operations that I do I have 2 more integer arraylists of equal sizes say 7 . something like this: B: [1,1,4,5,2,3,2] and C: [3,3,4,5,6,6,6]

I need help to compare the elements at indexes represented by arrayList: A in B and C seperately

Example:

compare elements in arrayList B at index [0,1] and check if list.get[0] == list.get[1] and for [4,5,6] check if list.get[4] == list.get[5] == list.get[6]

same for array list C

Any help much appreciated. Thanks in advance

Answer 1

Just as you would say it, use the values of arraylist A as indexes for the other lists:

Example A = [0,1] , B[3, 3]

You need to check if:

B[0] == B[1]

but rewriting the indexes as values of A you get:

B[A[0]] == B[A[1]]

Just extend this to the general case and you have solved the problem.

Answer 2

static boolean checkIndex ( List<List<Integer>> indexList, List<Integer> listToCheck ){
    for (List<Integer> indices : indexList) {
        int val = listToCheck.get( indices.get(0) );
        for (int i = 1; i < indices.size(); i++) {
            int index = indices.get(i);
            if ( listToCheck.get(index) != val ) {
                return false;
            }
        }
    }
    return true;
}

I would loop all index list and check for all values of the corresponding index in the other list.

Test

public static void main(String[] args) {
    List<List<Integer>> indexList = new ArrayList<>();
    indexList.add(Arrays.asList(0,1));
    indexList.add(Arrays.asList(4,5,6));
    System.out.println(indexList);
    List<Integer> tempList = Arrays.asList(1,1,4,5,2,3,2);
    List<Integer> tempList2 = Arrays.asList(3,3,4,5,6,6,6);
    System.out.println(tempList);
    System.out.println(checkIndex( indexList, tempList));
    System.out.println(tempList2);
    System.out.println(checkIndex( indexList, tempList2));
}

//Output

[[0, 1], [4, 5, 6]]
[1, 1, 4, 5, 2, 3, 2]
false
[3, 3, 4, 5, 6, 6, 6]
true