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MatrixUtil.java
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package com.thealgorithms.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);
}
}
}