Q5.java

//.Problem statement
//        For a given two-dimensional square matrix of size (N x N). Find the total sum of elements on both the diagonals and at all the four boundaries.
//
//        Sample input 1:
//        1
//        3
//        1 2 3
//        4 5 6
//        7 8 9
//        Sample Output 1:
//        45
//        Explanation for Sample Output 1:
//        The boundary elements are 1, 2, 3, 6, 9, 8, 7 and 4.
//
//        The first-diagonal elements are 1, 5 and 9.
//
//        The second-diagonal elements are 3, 5 and 7.
//
//        We just need to add all these numbers making sure that no number is added twice. For example, '1' is both a boundary element and a first-diagonal element similarly, '5' contributes to both the diagonals but they won't be added twice.
//
//        Hence, we add up, [1 + 2 + 3 + 6 + 9 + 8 + 7 + 4 + 5] to give 45 as the output.
package DAY_3;

import java.util.Scanner;

public class Q5
{
    public static void main(String[] args)
    {
        Scanner sc= new Scanner(System.in);
        System.out.println("Enter the rows and columns");

        int n=sc.nextInt();
        int arr[][]=new int[n][n];

        for(int i=0;i<n;i++)
        {
            for(int j=0;j<n;j++)
            {
                arr[i][j]=sc.nextInt();
            }
        }
        int sum=0;
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<n;j++)
            {
//                if(i==j)
//                {
//                    sum=sum+arr[i][j];
//                }
//                else if(i+j==2)
//                {
//                    sum=sum+arr[i][j];
//                }
                if(i==j||(i+j+1==n-1)||i==0||j==0||i==n-1||j==n-1)
                {
                    sum=sum+arr[i][j];
                }
            }

        }
        System.out.println(sum);
    }
}