diff --git a/Maths/MatrixUtil.java b/Maths/MatrixUtil.java new file mode 100644 index 000000000000..c598c6534c51 --- /dev/null +++ b/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 operate(final BigDecimal[][] matrix1, + final BigDecimal[][] matrix2, + final BiFunction 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 add(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) { + return operate(matrix1, matrix2, BigDecimal::add); + } + + public static Optional subtract(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) { + return operate(matrix1, matrix2, BigDecimal::subtract); + } + + public static Optional 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); + } + } +}