Matrix Multiply Math works

README.md

@@ -17,8 +17,7 @@ Dateien wie Bilder die zur Lösung einer Aufgabe gehören sind in <br><ins>Medie
 ## Angefangene unfertige Lösungen:
 - Damenproblem: VL 5 Aufgabe 2
 <br>Nicht die gewünschte rekursive Backtracking-Implementierung
-- Erweiterung Matrix-Klasse: VL 8 Aufgabe 3
-<br>Mathematisch falsche Lösung
+
 
 - Keine
 ## Fragen

src/part4/aufg3.java

@@ -9,7 +9,7 @@ public class aufg3 {
     // =====================
 
     public static void main(String[] args){
-        int MAXIMUM = 100_000_000;  // takes about 13 seconds(!!)
+        int MAXIMUM = 10_000_000;  // takes about 13 seconds(!!)
         int MAX_PER_ROW = 20;
 
         boolean[] primes = new boolean[MAXIMUM];

src/part6/aufg3.md

@@ -16,7 +16,7 @@
 ## Class Stringbuffer
 Ein String Buffer ist wie ein gewöhnlicher String eine Anreihung von Characters, jedoch können Länge und Inhalt eines String Buffers mithilfe von verschiedenen Methoden modifiziert werden.
 
-## Class String
+## Class Array
 ### Usefull Methods
 - equals() <br>Returns a Boolean value representing if two given Arrays are equal to one another.
 - fill() <br>Assigns a value to each element of the array.

src/part8/aufg2/Anwendung.java

@@ -9,5 +9,8 @@ public class Anwendung {
         road_boat.move();
         road_boat.bucketBilgeWater();
         road_boat.makeDust();
+
+        System.out.println(road_boat.seats);
+        System.out.println(road_boat.driverPosition);
     }
 }

src/part8/aufg2/vehicles/Amphibienfahrzeug.java

@@ -10,7 +10,6 @@ public class Amphibienfahrzeug implements Landfahrzeuge, Wasserfahrzeuge{
         System.out.println("I am zooming around");
     }
 
-
     public void bucketBilgeWater() {
         System.out.println("We are dry again");
     }

src/part8/aufg3/matrix.java

@@ -1,30 +1,30 @@
 package part8.aufg3;
 
 public class matrix {
-    private int rows;
-    private int cols;
+    private int numberOfRows;
+    private int numberOfCols;
     int[][] field;
 
-    matrix(int rows, int cols){
-        this.rows = rows;
-        this.cols = cols;
+    matrix(int numberOfRows, int numberOfCols){
+        this.numberOfRows = numberOfRows;
+        this.numberOfCols = numberOfCols;
 
-        field = new int[rows][cols];
+        field = new int[numberOfRows][numberOfCols];
     }
 
-    public int getCols() {
-        return cols;
+    public int getNumberOfCols() {
+        return numberOfCols;
     }
 
-    public int getRows() {
-        return rows;
+    public int getNumberOfRows() {
+        return numberOfRows;
     }
 
     void print(){
-        for (int i=0; i<this.rows; i++){
-            for (int j=0; j<this.cols; j++){
+        for (int i = 0; i<this.numberOfRows; i++){
+            for (int j = 0; j<this.numberOfCols; j++){
                 System.out.print(field[i][j]);
-                if (j != this.cols-1) {
+                if (j != this.numberOfCols -1) {
                     System.out.print(" ; ");
                 }
             }
@@ -37,18 +37,32 @@ public class matrix {
 
     int getValue(int row, int col){return field[row][col];}
 
+    public int[] getRow(int row){
+        return this.field[row];
+    }
+
+    public int[] getCol(int col){
+        int[] result = new int[this.getNumberOfRows()];
+
+        for (int i=0; i<this.getNumberOfRows(); i++){
+            result[i] = this.getValue(i, col);
+        }
+
+        return result;
+    }
+
     void scalarMultiply(int factor){
-        for (int i=0; i<this.rows; i++) {
-            for (int j = 0; j < this.cols; j++) {
+        for (int i = 0; i<this.numberOfRows; i++) {
+            for (int j = 0; j < this.numberOfCols; j++) {
                 field[i][j] *= factor;
             }
         }
     }
 
     void addMatrix(matrix matrix2){
-        for (int i=0; i<this.rows; i++) {
-            for (int j = 0; j < this.cols; j++) {
-                field[i][j] += matrix2.field[i][j];
+        for (int i = 0; i<this.numberOfRows; i++) {
+            for (int j = 0; j < this.numberOfCols; j++) {
+                this.field[i][j] += matrix2.field[i][j];
             }
         }
     }
@@ -56,10 +70,19 @@ public class matrix {
     boolean multiplyMatrix(matrix matrix2){
         boolean compatible = false;
 
-        if(this.getRows() == matrix2.getCols()){
+        if(this.getNumberOfRows() == matrix2.getNumberOfCols()){
             compatible = true;
-            matrix result = new matrix(this.getRows(), matrix2.getCols());
+            matrix result = new matrix(this.getNumberOfRows(), matrix2.getNumberOfCols());
 
+            for (int i=0; i<this.field.length; i++){
+                int[] currentRow = this.getRow(i);
+
+                for (int j=0; j<matrix2.field[0].length; j++){
+                    int[] currentCol = matrix2.getCol(j);
+                    int dotProduct = dotProduct(currentRow, currentCol);
+                    result.setValue(i,j,dotProduct);
+                }
+            }
 
             result.print();
         }
@@ -67,24 +90,58 @@ public class matrix {
         return compatible;
     }
 
+    private int dotProduct(int[] vector1, int[] vector2){
+        int result = 0;
+
+        if (vector1.length == vector2.length){
+            // do stuff
+            for (int i=0; i<vector1.length; i++){
+                result += vector1[i] * vector2[i];
+            }
+        }
+        else {
+            // Vectors not compatible Exception
+            // TODO
+        }
+        return result;
+    }
+
     public static void main(String[] args){
-        matrix nr1 = new matrix(2,3);
-        matrix nr2 = new matrix(2,3);
+//        matrix nr1 = new matrix(2,3);
+//        matrix nr2 = new matrix(2,3);
+//
+//        nr1.setValue(1,1,1);
+//        nr2.setValue(0,0,4);
+//
+//        nr2.addMatrix(nr1);
+//        nr2.print();
+//
+//        nr2.scalarMultiply(8);
+//        nr2.print();
+//
+//        nr2.scalarMultiply(7);
+//        nr2.print();
+//
+//        System.out.println("========================");
 
-        nr1.setValue(1,1,1);
-        nr2.setValue(0,0,4);
+        matrix nr3 = new matrix(2,3);
+        nr3.setValue(0,0,1);
+        nr3.setValue(0,1,2);
+        nr3.setValue(0,2,3);
+        nr3.setValue(1,0,4);
+        nr3.setValue(1,1,5);
+        nr3.setValue(1,2,6);
+        nr3.print();
 
-        nr2.addMatrix(nr1);
-        nr2.print();
+        matrix nr4 = new matrix(3,2);
+        nr4.setValue(0,0,7);
+        nr4.setValue(0,1,8);
+        nr4.setValue(1,0,9);
+        nr4.setValue(1,1,10);
+        nr4.setValue(2,0,11);
+        nr4.setValue(2,1,12);
+        nr4.print();
 
-        nr2.scalarMultiply(8);
-        nr2.print();
-
-        nr2.scalarMultiply(7);
-        nr2.print();
-
-        matrix nr3 = new matrix(7,4);
-        matrix nr4 = new matrix(6,7);
         System.out.println(nr3.multiplyMatrix(nr4));
     }
 }