[oubless]

Originally Posted by sania21

No it does not work if matrix is not a square matrix.

It works only on square matrix.

I want to implement it only on square matrix that can be of any dimension may be 50 by 50 but my coding should be limited.

package matrix;

import java.io.PrintStream;

public class Matrix {
	private double matrix[][];
	
	public Matrix(int rows, int cols){
		if( rows<1 || cols < 1)
			throw new IllegalArgumentException();
		matrix = new double[rows][cols];
	}
	
	public double get(int p,int q){
		return matrix[p][q];
	}
	
	public void set(int p,int q, double value){
		matrix[p][q] = value;
	}
	
	public Matrix invert(){
		//if not square - return null
		if( matrix.length != matrix[0].length )
			return null;
		Matrix result = new IMatrix(matrix.length);
		/*	 Starting row - from 0 to last	 */
		for(int startRow = 0; startRow < matrix.length; startRow++){
			/* divide all elements in that row on the first one */
			double divideOn = matrix[startRow][startRow];
			for(int col = startRow; col<matrix[startRow].length; col++){
				matrix[startRow][col] = matrix[startRow][col] / divideOn;
				result.matrix[startRow][col] = result.matrix[startRow][col] / divideOn;
			}
			//output
			display(System.out);
			result.display(System.out);
			/* for the rest of the rows: */
			for(int currentRow = startRow+1; currentRow < matrix.length; currentRow++){
				double multiplier = matrix[currentRow][startRow]; //take the first not 0 value
				for(int currentCol = startRow; currentCol<matrix[currentRow].length; currentCol++){
					matrix[currentRow][currentCol] = matrix[currentRow][currentCol] - multiplier*matrix[startRow][currentCol];
					result.matrix[currentRow][currentCol] = result.matrix[currentRow][currentCol] - multiplier*result.matrix[startRow][currentCol];
				}
				//output - after each row change
				display(System.out);
				result.display(System.out);
			}
		}
		return result;
	}
	
	public void display(PrintStream ps){
		for(double row[] : matrix){
			for( double d:row)
				ps.print(d+"\t");
			ps.println();
		}
		ps.println();
		ps.println();
	}
	
	public static void main(String args[]){
		Matrix m = new Matrix(3,3);
		m.set(0, 0, 4);
		m.set(0, 1, 2);
		m.set(0, 2, 2);
		
		m.set(1, 0, 4);
		m.set(1, 1, 6);
		m.set(1, 2, 8);
		
		m.set(2, 0, -2);
		m.set(2, 1, 2);
		m.set(2, 2, 4);
		
		m.invert().display(System.out);
	}
}

class IMatrix extends Matrix{
	public IMatrix(int side){
		super(side,side);
		for( int i=0; i<side;i++){
			super.set(i, i, 1.0);
		}
	}
}

try this one ... I hope it is what you want
Write if something is not ok