Hackerrank - Difference of Diagonals of an Array

 Given a square matrix, calculate the absolute difference between the sums of its diagonals.

For example, the square matrix  is shown below:

1 2 3
4 5 6
9 8 9

The left-to-right diagonal = . The right to left diagonal = . Their absolute difference is .

Function description

Complete the  function in the editor below.

diagonalDifference takes the following parameter:

  • int arr[n][m]: an array of integers

Return

  • int: the absolute diagonal difference

Input Format

The first line contains a single integer, , the number of rows and columns in the square matrix .
Each of the next  lines describes a row, , and consists of  space-separated integers .

Constraints

Output Format

Return the absolute difference between the sums of the matrix's two diagonals as a single integer.

Sample Input

3
11 2 4
4 5 6
10 8 -12

Sample Output

15

Explanation

The primary diagonal is:

11
   5
     -12

Sum across the primary diagonal: 11 + 5 - 12 = 4

The secondary diagonal is:

     4
   5
10

Sum across the secondary diagonal: 4 + 5 + 10 = 19
Difference: |4 - 19| = 15

Note: |x| is the absolute value of x

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 diagonalDifference(List<List<Integer>> arr) {
        int primaryDiag = 0;
        int secondaryDiag = 0;
        
        int i=0,j=0;
        
        while (i < arr.size()) {
            primaryDiag+= arr.get(i).get(i);
            i++;    
        }

        i = 0;j=0;
        
        while (i < arr.size()) {
            secondaryDiag+= arr.get(i).get(arr.size()-i-1);
            i++;    
        }


        
        return Math.abs(primaryDiag-secondaryDiag);
    }


}

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<List<Integer>> arr = new ArrayList<>();

        IntStream.range(0, n).forEach(i -> {
            try {
                arr.add(
                    Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
                        .map(Integer::parseInt)
                        .collect(toList())
                );
            } catch (IOException ex) {
                throw new RuntimeException(ex);
            }
        });

        int result = Result.diagonalDifference(arr);

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

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



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