Find Non-Divisible Subset from Given Array | BlogOnCode

Java Solution for finding Non Divisible Subset in Given Array

Problem Description :

Given a set of distinct integers, print the size of a maximal subset of S where the sum of any 2 numbers in S' is not evenly divisible by k.

Example 1 :

S = [19, 10, 12, 10, 24, 25, 22], k = 4

Output = 3

One of the arrays that can be created is S'[0] = [10, 12, 25] Another is S'[1] = [19, 22, 24]. After testing all permutations, the maximum length solution array has 3 elements.

Example 2 :

S = [1, 7, 2, 4], k = 3

Output = 3

[1, 7, 4]

Example 3 :

S = [278, 576, 496, 727, 410, 124, 338, 149, 209, 702, 282, 718, 771, 575, 436], k = 7

Output = 11

In simple word, we have to find maximum subset of current array where it can not be divisible by given k.

Lets jump on code.

Solution 1 : Java Solution for finding Non Divisible Subset in Given Array

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;

class Result {

    public static int nonDivisibleSubset(int k, List<Integer> list) {
        
        int[] remainderCount = new int[k];
       
        for (int i = 0; i < list.size(); i++) {
          remainderCount[list.get(i) % k]++;
        }

        int result = 0;
        for (int i = 1; i <= k / 2; i++) {
          if (i != k - i) {
            result += Math.max(remainderCount[i], remainderCount[k - i]);
          } else {
            result++;
          }
        }

        result += Math.min(remainderCount[0], 1);
        return result;

    }
}

public class Solution {
    public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        String[] firstMultipleInput = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");

        int n = Integer.parseInt(firstMultipleInput[0]);

        int k = Integer.parseInt(firstMultipleInput[1]);

        List<Integer> s = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
            .map(Integer::parseInt)
            .collect(toList());

        int result = Result.nonDivisibleSubset(k, s);

        bufferedWriter.write(String.valueOf(result));
        bufferedWriter.newLine();

        bufferedReader.close();
        bufferedWriter.close();
    }
}

Solution Explanation :

Here we are storing remainder count of all given list value into array.

• First store all remainder total count of given list in array.
•  S = [19, 10, 12, 10, 24, 25, 22], k = 4
•  remainderCount = [2, 1, 3, 1, 0, 0, 0]
•  Then add another count value into result whose value does not divisible by given k.
• Last return result.

 

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