Thread: Diagonal of a matrix usind a 2d int array

Hello!

Implement a method that finds the digonal of a matrix.Use the method as given;

static int[] diagonal(int[][] a) {..} the method should return the diagonal a in the form of an int array.

So what I've tried is this

 
public class test {
 
	static int[] diagonal (int[][] a) {
		for(int i = 0; i<a.length; i++) {
			for(int j = 0; i<a.length; j++) {
 
				if( i = j) {
					a =[i][j];
				}
			}
		}
		return a;
	}
public static void main(String[] args){
	int[][] a = {{1,2,3,4}};
 
	diagonal(a);
}
}

test.java:8: error: illegal start of expression
a =[i][j];

is the error I get when I try to compile.I think I know how to get the diagonal,we need 2 for loops to go through the array and we check the value if they match we found it. The part that is bugging me is I dont know how to transfer that into an int array and return it like I'm susposed to.

Any tips?

Okay so I'll try to explain what I want to do exacly. We need to able to find the diagonal of a quadratic matrix (the matrix which has the same number of rows and coloumns).To do that I'm giving a static method int[] diagonal(int[][] a) {..} The method is of type int arrray and the parameter is a 2d int array. What I had in mind.

What we need to achive is this.Lets assume our matrix looks like this. { 1 2 3
4 5 6
3 4 5}

The goal is that the diagonal of the matrix a is returend as an int array. in this case that would be {1 5 5},

So here is my though process (a bit revised). We need 2 for loops that will go through the matrix a.Meaning from the first to the last element in the array.Than after moving through the array we need to check if the values are in a diagonal and than we need to save those values(the diagonal) in an int array and return it.I've realised my first attempt was kind of nonsence.

import java.util.Arrays;
public class test {
 
 
	static int[] getDiagonal(int[][] a) {
		int diagonal[] = new int[a.length];
		for(int i = 0; i<diagonal.length; i++) {
			diagonal[i] = a[i][i];
		}
		Out.println(Arrays.toString(diagonal));
		return diagonal;
 
	}
 
	public static void main(String[] args) {
		int[][] rnd_array = {{1,2,4},{6,7,3}};
 
		getDiagonal(rnd_array);
	}
}

The code compiles fine,but it isnt working properly.It only prints out 1 and 7.What am I missing here.

Oh wow,that is embarassing,quite a silly mistake.It works just fine now thank you!