Add MatrixUtil for matrix operations

Maths/MatrixUtil.java

@@ -0,0 +1,169 @@
+package Maths;
+
+import java.math.BigDecimal;
+import java.util.Arrays;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.function.BiFunction;
+import java.util.stream.IntStream;
+
+/**
+ * @author: caos321
+ * @date: 31 October 2021 (Sunday)
+ */
+public class MatrixUtil {
+
+    public static boolean isValid(final BigDecimal[][] matrix) {
+        return matrix != null && matrix.length > 0 && matrix[0].length > 0;
+    }
+
+    public static boolean hasEqualSizes(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
+        return isValid(matrix1) && isValid(matrix2)
+                && matrix1.length == matrix2.length
+                && matrix1[0].length == matrix2[0].length;
+    }
+
+    public static boolean canMultiply(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
+        return isValid(matrix1) && isValid(matrix2)
+                && matrix1[0].length == matrix2.length;
+    }
+
+    public static Optional<BigDecimal[][]> operate(final BigDecimal[][] matrix1,
+                                                   final BigDecimal[][] matrix2,
+                                                   final BiFunction<BigDecimal, BigDecimal, BigDecimal> operation) {
+        if (!hasEqualSizes(matrix1, matrix2)) {
+            return Optional.empty();
+        }
+
+        final int rowSize = matrix1.length;
+        final int columnSize = matrix1[0].length;
+
+        final BigDecimal[][] result = new BigDecimal[rowSize][columnSize];
+
+        IntStream.range(0, rowSize).forEach(rowIndex ->
+                IntStream.range(0, columnSize).forEach(columnIndex -> {
+                    final BigDecimal value1 = matrix1[rowIndex][columnIndex];
+                    final BigDecimal value2 = matrix2[rowIndex][columnIndex];
+
+                    result[rowIndex][columnIndex] = operation.apply(value1, value2);
+                }));
+
+        return Optional.of(result);
+    }
+
+    public static Optional<BigDecimal[][]> add(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
+        return operate(matrix1, matrix2, BigDecimal::add);
+    }
+
+    public static Optional<BigDecimal[][]> subtract(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
+        return operate(matrix1, matrix2, BigDecimal::subtract);
+    }
+
+    public static Optional<BigDecimal[][]> multiply(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
+        if (!canMultiply(matrix1, matrix2)) {
+            return Optional.empty();
+        }
+
+        final int size = matrix1[0].length;
+
+        final int matrix1RowSize = matrix1.length;
+        final int matrix2ColumnSize = matrix2[0].length;
+
+        final BigDecimal[][] result = new BigDecimal[matrix1RowSize][matrix2ColumnSize];
+
+        IntStream.range(0, matrix1RowSize).forEach(rowIndex ->
+                IntStream.range(0, matrix2ColumnSize).forEach(columnIndex ->
+                        result[rowIndex][columnIndex] = IntStream.range(0, size).mapToObj(index -> {
+                                    final BigDecimal value1 = matrix1[rowIndex][index];
+                                    final BigDecimal value2 = matrix2[index][columnIndex];
+
+                                    return value1.multiply(value2);
+                                })
+                                .reduce(BigDecimal.ZERO, BigDecimal::add)
+                )
+        );
+
+        return Optional.of(result);
+    }
+
+    public static void assertThat(final BigDecimal[][] actual, final BigDecimal[][] expected) {
+        if (!Objects.deepEquals(actual, expected)) {
+            throw new AssertionError(String.format(
+                    "expected=%s but was actual=%s",
+                    Arrays.deepToString(expected),
+                    Arrays.deepToString(actual)
+            ));
+        }
+    }
+
+    public static void main(final String[] args) {
+        {
+            final BigDecimal[][] matrix1 = {
+                    {new BigDecimal(3), new BigDecimal(2)},
+                    {new BigDecimal(0), new BigDecimal(1)},
+            };
+
+            final BigDecimal[][] matrix2 = {
+                    {new BigDecimal(1), new BigDecimal(3)},
+                    {new BigDecimal(2), new BigDecimal(0)},
+            };
+
+            final BigDecimal[][] actual = add(matrix1, matrix2)
+                    .orElseThrow(() -> new AssertionError("Could not compute matrix!"));
+
+            final BigDecimal[][] expected = {
+                    {new BigDecimal(4), new BigDecimal(5)},
+                    {new BigDecimal(2), new BigDecimal(1)}
+            };
+
+            assertThat(actual, expected);
+        }
+
+        {
+            final BigDecimal[][] matrix1 = {
+                    {new BigDecimal(1), new BigDecimal(4)},
+                    {new BigDecimal(5), new BigDecimal(6)},
+            };
+
+            final BigDecimal[][] matrix2 = {
+                    {new BigDecimal(2), new BigDecimal(0)},
+                    {new BigDecimal(-2), new BigDecimal(-3)},
+            };
+
+            final BigDecimal[][] actual = subtract(matrix1, matrix2)
+                    .orElseThrow(() -> new AssertionError("Could not compute matrix!"));
+
+            final BigDecimal[][] expected = {
+                    {new BigDecimal(-1), new BigDecimal(4)},
+                    {new BigDecimal(7), new BigDecimal(9)}
+            };
+
+            assertThat(actual, expected);
+        }
+
+        {
+            final BigDecimal[][] matrix1 = {
+                    {new BigDecimal(1), new BigDecimal(2), new BigDecimal(3)},
+                    {new BigDecimal(4), new BigDecimal(5), new BigDecimal(6)},
+                    {new BigDecimal(7), new BigDecimal(8), new BigDecimal(9)}
+            };
+
+            final BigDecimal[][] matrix2 = {
+                    {new BigDecimal(1), new BigDecimal(2)},
+                    {new BigDecimal(3), new BigDecimal(4)},
+                    {new BigDecimal(5), new BigDecimal(6)}
+            };
+
+            final BigDecimal[][] actual = multiply(matrix1, matrix2)
+                    .orElseThrow(() -> new AssertionError("Could not compute matrix!"));
+
+            final BigDecimal[][] expected = {
+                    {new BigDecimal(22), new BigDecimal(28)},
+                    {new BigDecimal(49), new BigDecimal(64)},
+                    {new BigDecimal(76), new BigDecimal(100)}
+            };
+
+            assertThat(actual, expected);
+        }
+    }
+}