https://www.hackerrank.com/challenges/minimum-absolute-difference-in-an-array/problem?h_l=interview&playlist_slugs%5B%5D=interview-preparation-kit&playlist_slugs%5B%5D=greedy-algorithms

MinimumAbsoluteDifferenceInAnArray.java

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 {

    /*
     * Complete the 'minimumAbsoluteDifference' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts INTEGER_ARRAY arr as parameter.
     */

    public static int minimumAbsoluteDifference(List<Integer> arr) {
        Collections.sort(arr);
        int min = Integer.MAX_VALUE;
        for (int i =0; i<arr.size()-1; i++){
            int difference = Math.abs(arr.get(i) - arr.get(i+1));
            if ( difference < min){
                min = difference;
            }
/*            
            for (int j=i+1; j<arr.size()/2; j++){
                int difference = Math.abs(arr.get(i) - arr.get(j));
                if ( difference < min){
                    min = difference;
                }
            }
            */
        }
        return min;
    }

}

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")));

        int n = Integer.parseInt(bufferedReader.readLine().trim());

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

        int result = Result.minimumAbsoluteDifference(arr);

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

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

2' for the first version (O(n*n)), 7' to optimize (O(n+n ln(n)))