CODEWITHSUNDEEP
javadata-structuresmapping
Paul
Paul

Reputation: 1149

Java datastructure to hold a value mapped to an array

I am kind of lost on which data structure to use to solve my problem effectively. I want to map an array to a value. What I mean is that if I have 1000 values, I need to be able to map multiple other values to each of the 1000 values.

For example,

I have 1000 A values from 1-1000. For each value A, I want to map k other values B (these range from 1-1000 also). But I do want to ensure that whatever values are mapped to A are not duplicates. Mapped values between different A values can be the same (i.e. both 2 and 1000 have 67 mapped to them).

    1 -> 138, 92, 835, 841, 12
    2 -> 766, 324, 26, 933, 62
    3 -> 53, 131, 62, 121, 67
    4->160, 160 #NOT OK
    4-> 162, 171, 594, 912, 455
    ...
    1000->146, 981, 67, 246, 146

So when I look at some arbitrary value A, I should be easily able to identify whatever values are mapped to it. So if I wanted to access value 3, I should be able to print out both the value A (3) and its associated values (53, 131, 62, 121, 67).

I hope that makes sense. What would be the best way of achieving this kind of data structure? Any help of an explanation or an example would be much appreciated.

Upvotes: 0

Views: 125

Answers (3)

PaulProgrammer
PaulProgrammer

Reputation: 17630

You want an array list of sets:

ArrayList<Set<Long>>

Set requires that the value is in the collection once and only once, and of course the list is a list of these collections.

You can then use the get(index) method on ArrayList to get specific ordinals.

ArrayList<Set<Number>> mappings = new ArrayList<Set<Long>>();

Set<Long> s = new HashSet<Long>();
long[] n = {138, 92, 835, 841, 12};
s.addAll( Arrays.toList( n));
mappings.add(1, s);
// etc.

Later, to fetch:

Set<Long> result = mappings.get(1); // for element in slot 1...

Upvotes: 1

Bohemian
Bohemian

Reputation: 424993

if you have continuous values (or even near-continuous), you don't need to "map" then - you can use a simple array of array:

int[][] a = new int[1001][];

then for each value, create an array of int:

a[1] = new int[]{138, 92, 835, 841, 12};

etc

Upvotes: 0

Jigar Joshi
Jigar Joshi

Reputation: 240880

Use

Map<Long, Set<Long>> numberToValuesMap;

Set for uniqueness

Upvotes: 2

Related Questions