對角線差（Diagonal Difference）

題目：

給出一個N*N的二維整數數組，計算主對角線元素和和副對角線和之間的差。

Sample Input

3
11 2 4
4 5 6
10 8 -12

Sample Output

15

我的解答：

import java.io.*;
import java.util.*;

public class DiagonalDifference{
	public static void main(String[] args){

		//input
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		scan.nextLine();
		int arr[][] = new int[N][N];
		for(int i = 0; i < N; i++){
			for(int j = 0; j < N;j++){
				arr[i][j] = scan.nextInt();
			}

			if(scan.hasNextLine()){ // 如果不寫這一行就會
				scan.nextLine();	
			}
		}

		//calculate
		int primaryDiagonal = 0;
		for(int i = 0 ; i < N; i++){
			primaryDiagonal += arr[i][i];
		}

		int secondaryDiagonal = 0;
		for(int i = 0; i < N; i++){
			secondaryDiagonal += arr[i][N - i - 1];
		}

		int result = primaryDiagonal - secondaryDiagonal;
		result = (result < 0) ? (-result) : result;
		System.out.println(result);
		scan.close();
	}
}