CODEWITHSUNDEEP
javaalgorithmsortingcounting-sort
Hardik Vats
Hardik Vats

Reputation: 57

Variant of Counting sort /Sorting algorithm

there is a problem which gives me a random number as a pivot, and i have to sort my array w.r.t to this pivot (closest come first then farthest) for e.g. 

array =[2,7,4,6,4,4,5,3,6,9,1,1,9] and 

    pivot=5 

    expected output: [5,4,4,6,6,3,7,2,1,1,9,9]

is this a variation of counting sort by any chance? if not ! can anyone give me a clue towards solving this problem? I am encountering a roadblock in thinking on how to handle the counts and the array indices Therefore, so far i have been able to do this

class HelloEclipse{

public static void main(String[] args) {
    Scanner sc=new Scanner(System.in);
    int N=sc.nextInt();
    int pivot=sc.nextInt();
    int[] mainArray=new int[N];
    int[] differenceArray=new int[N];
    int[] differnceCountArray=new int[Integer.MAX_VALUE];
    for(int i=0;i<N;i++){
        mainArray[i]=sc.nextInt();
        differenceArray[i]=pivot-mainArray[i];
        if(differenceArray[i]>0){
        differnceCountArray[differenceArray[i]]++;}
        else{
            differnceCountArray[-differenceArray[i]]++;
        }

    }
    }
}

Any suggestions on how to proceed will be helpful!

Upvotes: 0

Views: 360

Answers (2)

Turo
Turo

Reputation: 4914

Write a suitable Integer-Comparator and use Arays.sort:

public class PivotComparator implements Comparator<Integer> {

    private int pivot;

    public PivotComparator(int pivot) {
        super();
        this.pivot = pivot;
    }

    @Override
    public int compare(Integer a, Integer b) {
        return Math.abs(a - pivot) - Math.abs(b - pivot);
    }

    public static void main(String[] args) {

        Integer[] toSort = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };

        Comparator<Integer> comp = new PivotComparator(5);

        Arrays.sort(toSort, comp);
        for (Integer i : toSort) {
            System.out.println(i);
        }

    }

}

EDIT

to get all the fours in front of the sixes you could do(instead of sorting twice)

public int compare(Integer a, Integer b) {
    int diff = Math.abs(a - pivot) - Math.abs(b - pivot);
    if (diff != 0) {
        return diff;
    }
    return a - b;
}

Upvotes: 2

Saravana
Saravana

Reputation: 12817

Here is an implementation

    int[] array = { 2, 7, 4, 6, 4, 4, 5, 3, 6, 9, 1, 1, 9 };
    int pivot = 5;
    int[] sorted = Arrays.stream(array).boxed().sorted().sorted((i1, i2) -> Math.abs(i1 - pivot) - Math.abs(i2 - pivot)).mapToInt(i -> i).toArray();
    System.out.println(Arrays.toString(sorted));

output

[5, 4, 4, 4, 6, 6, 3, 7, 2, 1, 1, 9, 9]

Upvotes: 0

Related Questions