Data update

Task/Reduced-row-echelon-form/Java/reduced-row-echelon-form-2.java

@@ -0,0 +1,85 @@
+import java.util.List;
+
+public final class ReducedRowEchelonForm {
+
+	public static void main(String[] args) {
+		double[][] first = new double[][] { {   1.0,   2.0,  -1.0,  -4.0 },
+		                                    {   2.0,   3.0,  -1.0, -11.0 },
+		                                    {  -2.0,   0.0,  -3.0,  22.0 } };
+		
+		double[][] second = new double[][] { { 1.0,  2.0,  3.0,  4.0,  3.0,  1.0 },
+	           							     { 2.0,  4.0,  6.0,  2.0,  6.0,  2.0 },
+	           						         { 3.0,  6.0, 18.0,  9.0,  9.0, -6.0 },
+	           							     { 4.0,  8.0, 12.0, 10.0, 12.0,  4.0 },
+	           							     { 5.0, 10.0, 24.0, 11.0, 15.0, -4.0 } };
+	           							
+	    List.of( first, second ).forEach( m -> {
+	    	display("Original matrix:", m);
+	    	display("Reduced row echelon form:", reducedRowEchelonForm(m));
+	    } );
+	}
+	
+	private static double[][] reducedRowEchelonForm(double[][] matrix) {	
+	    final int rowCount = matrix.length;
+	    final int colCount = matrix[0].length;
+	
+	    int lead = 0;	
+	    for ( int row = 0; row < rowCount; row++ ) {
+	        if ( colCount <= lead ) {
+	            return matrix;
+	        }
+	
+	        int ro = row;
+	        while ( matrix[ro][lead] == 0.0 ) {
+	            ro += 1;
+	            if ( rowCount == ro ) {
+	                ro = row;
+	                lead += 1;
+	                if ( colCount == lead ) {
+	                    return matrix;
+	                }
+	            }
+	        }
+	
+	        final double[] temp = matrix[row];
+			matrix[row] = matrix[ro];
+			matrix[ro] = temp;	
+	
+	        if ( matrix[row][lead] != 0.0 ) {
+	        	final double divisor = matrix[row][lead];
+	        	for ( int co = 0; co < matrix[0].length; co++ ) {
+	    			matrix[row][co] /= divisor;
+	    		}
+	        }
+	
+	        for ( int j = 0; j < rowCount; j++ ) {
+	            if ( j != row ) {
+	            	final double multiple = matrix[j][lead];
+	            	for ( int co = 0; co < matrix[0].length; co++ ) {
+	        			matrix[j][co] -= matrix[row][co] * multiple;
+	        		}
+	        	}
+	        }
+	        lead += 1;
+	    }
+	    return matrix;
+	}
+
+	private static void display(String title, double[][] matrix) {
+	    System.out.println(title);
+	    final int rowCount = matrix.length;
+	    final int colCount = matrix[0].length;
+
+	    for ( int row = 0; row < rowCount; row++ ) {
+	        for ( int col = 0; col < colCount; col++ ) {
+	            if ( matrix[row][col] == -0.0 ) {
+	            	matrix[row][col] = 0.0;
+	            }
+	            System.out.print(String.format("%6.1f", matrix[row][col]));
+	        }
+	        System.out.println();
+	    }
+	    System.out.println();
+	}
+	
+}