Sort By Indices - JAVA

// Author : Saurav Kalsoor
// Sort By Indices - JAVA

import java.util.*;

public class Test {

    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        int n = sc.nextInt();
        int m = sc.nextInt();
        ArrayList<Integer> arr = new ArrayList<>();
        ArrayList<Integer> indices = new ArrayList<>();

        for(int i=0; i < n; i++) {
            int input = sc.nextInt();
            arr.add(input);
        }

        for(int i=0; i < m; i++) {
            int input = sc.nextInt();
            indices.add(input);
        }

        ArrayList<Integer> result = sortByIndices(arr, indices, n, m);

        for(int i=0; i < n; i++)
            System.out.print(result.get(i) + " ");

        System.out.println();
    }

    public static ArrayList<Integer> sortByIndices(ArrayList<Integer> arr, ArrayList<Integer> indices, int n, int m){
        ArrayList<Integer> sortDesc = new ArrayList<Integer>();
        ArrayList<Integer> sortAsc = new ArrayList<Integer>();

        HashSet<Integer> indicesSet = new HashSet<Integer>();

        for(int i=0; i < m; i++){
            indicesSet.add(indices.get(i));
        }

        for(int i=0; i < n; i++){
            if(indicesSet.contains(i)){
                sortDesc.add(arr.get(i));
            }else{
                sortAsc.add(arr.get(i));
            }
        }

        Collections.sort(sortDesc, Collections.reverseOrder());
        Collections.sort(sortAsc);

        ArrayList<Integer> result = new ArrayList<Integer>();

        int j = 0, k = 0;
        for(int i=0; i < n; i++){
            if(indicesSet.contains(i)){
                result.add(sortDesc.get(j));
                j++;
            }else{
                result.add(sortAsc.get(k));
                k++;
            }
        }

        return result;
    }
}