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multiplyメソッドを使うコードを追加

2021/07/05 10:01

投稿

kazuma-s

スコア8224

test CHANGED Viewed

@@ -141,3 +141,165 @@
 }
 ```
+**追記**
+行列の掛け算をコンストラクタで実行するのではなく、
+a.multiply(b) で結果の Matrix を返してくれるようにしてみました。
+```Java
+import java.io.*;
+public class Matrix {
+    private int row, col;
+    private double[][] matrix;
+	public Matrix() {}
+	public Matrix(int row, int col) {
+		this.row = row;
+		this.col = col;
+		matrix = new double[row][col];
+	}
+    public void read(String filename) {
+        try (BufferedReader br = new BufferedReader(new FileReader(filename))){
+            String[] rowcol = br.readLine().split(" ");
+            row = Integer.parseInt(rowcol[0]);
+            col = Integer.parseInt(rowcol[1]);
+            matrix = new double[row][col];
+            for (int m = 0; m < row; m++) {
+                String[] record = br.readLine().split(" ");
+                for (int n = 0; n < col; n++)
+                    matrix[m][n] = Double.parseDouble(record[n]);
+            }
+        }
+        catch (FileNotFoundException e) {
+            e.printStackTrace();
+        }
+        catch (IOException e) {
+            e.printStackTrace();
+        }
+        catch (NumberFormatException e) {
+            e.printStackTrace();
+        }
+    }
+    public void print() {
+        for (int i = 0; i < row; i++) {
+            for (int j = 0; j < col; j++)
+                System.out.print(" " + matrix[i][j]);
+            System.out.println();
+        }
+        System.out.println();
+    }
+    public Matrix multiply(Matrix b) {
+        if (col != b.row) return null;
+		Matrix c = new Matrix(row, b.col);
+		for (int i = 0; i < row; i++)
+			for (int j = 0; j < col; j++) {
+				c.matrix[i][j] = 0;
+				for (int k = 0; k < b.row; k++)
+					c.matrix[i][j] += matrix[i][k] * b.matrix[k][j];
+			}
+		return c;
+    }
+    public static void main(String[] args){
+        if (args.length != 2) {
+            System.out.println("need two files");
+            System.exit(1);
+        }
+        Matrix a = new Matrix();
+        a.read(args[0]);
+        a.print();
+        Matrix b = new Matrix();
+        b.read(args[1]);
+        b.print();
+        Matrix c = a.multiply(b);
+        c.print();
+    }
+}
+```