在Java中将矩阵的对角线值相乘

Question

I want to multiply 2 diagonals of a Matrix. But i am not able to get the diagonals of matrix. like in given code two diagonals are d1=5*5*9 . and d2=3*5*7 then i will use d1 and d2 values for further process.

How to do it. Note: matrix size can be different like here its 3x3 but it can be 5x5

private static int diagonalMultiply(int [][]arr1){
    int[][]  arr= {
       {5,2,3},
       {4,5,6},    
       {7,8,9}
   };
for ( int x = 0; x < arr.length; x++) //stepping along the x axis again.
{
    for ( int y = 0; y < arr[x].length; y++) // stepping along the y axis.
    {
        System.out.print(arr[x][y]+" ");
    }    
}
    return 0;
}

Answer 1

A diagonal of an N×N matrix has N elements. A pair of nested loops, each going from 0 to N-1 , cover N ² elements. This means that you need one loop, not two.

Both diagonals can be retrieved in a single loop. Indexes of the descending diagonal are (i, i) , while indexes of the ascending one are (Ni-1, i) :

int N = arr.length;
for ( int i = 0; i < N ; i++) {
    System.out.println(arr[i][i]+" "+arr[N-i-1][i]);
}

Demo.