根据特定条件分割地图

Question

I have a map as shown below:

Key        Value
    23      20
    32      20      (20+20  =40 , min=23 max=32)
    43      18
    45      24      (24+18 =42 , since 42 >40 so here min and max will be same that is 43
    47      10    
    56      6       (24 +10 +6 =40) so here min =45 and max = 56
    49       2  
    47      12  

As you can see, there will be final constant named split whose value is 40

final int SPLIT = 40;  //this will be configurable as it value can be changed.

I have to implement the logic such as if the value of the map reaches 40, then the first key of the map from where the calculation started and the key where exactly it reaches to 40 will be chosen as min and max also, as explained above.

Besides this, care needs to be taken if sum reaches more than 40. If so, we have to ignore it and take the previous value itself as min and max in the case where min and max would be equal.

Please suggest me how can I achieve this with Java and Map . folks please advise

The data that I am geeting is not from database I am geeting it from hibernate criteria in an object list

I am getting an list from Hibernate criteria as shown below ...

  List<Object[]> abcObjectsList= session.createCriteria(dddObject.class) 

upon inspecting while I am getting data in this format

abcObjectsList= ArrayList<E>
     elementData =Object[3]
        [0] = Long  ----------> value 23
        [1] = Integer -------> value 20
        [0] = Long  ----------> value 32
        [1] =Integer -------> value 20
        [0] =Long  ----------> value 43
        [1] =Integer -------> value 18

I have stored it in a map in such a way as I was requiring it in same fashion

  Map<Long, Integer> result = new HashMap<Long, Integer>();
            for (Object[] arr : list) {
                result.put((Long) arr[0], (Integer) arr[1]);
            }

so finally map will contain..

  Key      Value
        23      20
        32      20  (20+20  =40 , min=23 max=32)
        43      18

Answer 1

Instead of using a Map, you could create a Pair class that will hold the key and the value.

class Pair {
    public int key;
    public int value;

    public Pair(int key, int value){
        this.key = key;
        this.value = value;
    }
}

Then create a list of pair and iterate through it. If the sum is 0, initialize the min and the max. Then for each pair iterated, add its value to the sum. If the sum is inferior continue the loop and update the max key, else you have two cases possible:

1. The sum is equals to the limit so update the max key
2. The sum is not equals to the limit (so it's superior), decrement the index and don't update the max key

---

public static void main(String[] arg) {
    List<Integer> indexList = Arrays.asList(23,32,43,45,47,56,49,47); // get this from database
    List<Integer> valueList = Arrays.asList(20,20,18,24,10,6,2,12); // get this from database
    List<Pair> pairList = new ArrayList<>();
    for(int i = 0; i < indexList.size();i++){
        pairList.add(new Pair(indexList.get(i), valueList.get(i)));
    }
    int sum = 0;
    int min = -1;
    int max = -1;

    for(int i = 0; i < pairList.size(); i++){
        Pair p = pairList.get(i);
        if(sum == 0){
            min = p.key;
            max = p.key;
        }
        sum += p.value;
        if(sum < LIMIT){
            max = p.key;
        } else {
            if(sum > LIMIT){
                i--;
            } else {
                max = p.key;
            }
            System.out.println(min+"_"+max);
            sum = 0;
        }
    }
}

Which prints:

23_32
43_43
45_56

I show you how to create a list of pair through your map (use a LinkedHashMap to preserve insertion order) (obviously, you'll need to modify a little bit the Pair class):

Map<Long, Integer> m = new LinkedHashMap<>();
//fill your map here
List<Pair> l = new ArrayList<>();
for(Map.Entry<Long, Integer> entries : m.entrySet()){
    l.add(new Pair(entries.getKey(), entries.getValue()));
}
//Now you have a list of Pair