如何在Java中获得两个n维数组的总和？

Question

在Java中添加两个n维数组

addVectors

可以像这样添加Java中的两个1维数组/向量：

public static int[] addVectors( int[] a, int[] b )
{
    int[] c = new int[a.length];

    for ( int i = 0; i < a.length; i++ )
    {
        c[i] = a[i] + b[i];
    }

    return c;
}

addMatrices

可以像这样添加Java中的两个二维数组/矩阵：

public static int[][] addMatrices( int[][] a, int[][] b )
{
    int[][] c = new int[a.length][a[0].length];

    for ( int i = 0; i < a.length; i++ )
    {
        c[i] = addVectors( a[i], b[i] );
    }

    return c;
}

这两个函数都要求数组具有相同的大小，以避免arrayOutOfBoundsException 。

addArraysN

应该有一种方法可以使用递归添加两个未知维度的数组。
例如，以下代码使用假设函数addArraysN( arr1, arr2 )

int[][][] a = { 
                { { 1, 1, 1 }, { 1, 1, 1 }, { 1, 1, 1 } },
                { { 1, 1, 1 }, { 1, 1, 1 }, { 1, 1, 1 } },
                { { 1, 1, 1 }, { 1, 1, 1 }, { 1, 1, 1 } }
              };
int[][][] b = { 
                { { 2, 2, 2 }, { 2, 2, 2 }, { 2, 2, 2 } },
                { { 2, 2, 2 }, { 2, 2, 2 }, { 2, 2, 2 } },
                { { 2, 2, 2 }, { 2, 2, 2 }, { 2, 2, 2 } }
              };
int[][][] sum = addArraysN( a, b );
System.out.println( java.util.Arrays.deepToString( sum ) );

应该输出

[[[3, 3, 3], [3, 3, 3], [3, 3, 3]], [[3, 3, 3], [3, 3, 3], [3, 3, 3]], [[3, 3, 3], [3, 3, 3], [3, 3, 3]]]

现在我想知道如何实现这个函数addArraysN( arr1, arr2 ) 。
我开始使用以下伪代码：

addArraysN( arr1, arr2 )
{
    int dimension = getDimension( arr1 );
    if ( dimension == 0 ) //there are no arrays, only numbers
        return arr1 + arr2;
    else
    {
        //create a new arrays with the same dimension and size as arr1 / arr2
        //loop through the fields with for
            //call itself when adding the fields of arr1 and arr2
        //return the sum
    }
}

可以使用java.lang.reflect.Array中的newInstance -method创建新数组。
循环可以像这样：

for ( int i = 0; i < ((int[])arr1).length; i++ )
    sum = addArraysN( ((int[])arr1)[i], ((int[])arr2)[i] );

题

但我偶然发现了许多运行时错误和其他问题。 有没有人想到如何实现这个addArrayN -method的想法甚至解决方案？

它也应该可以使用ArrayList或任何其他类，但我主要感兴趣的是如何使用数组...（但如果有人知道它请发布！）

提前致谢

附录1

我原来的代码：

import java.util.Arrays;
import java.lang.reflect.Array;

public class ArrayN
{
    public static void main( String[] args )
    {
        //Vector
        int[] vector1 = {0, 1, 2, 3, 4};
        int[] vector2 = {4, 3, 2, 1, 0};

        int[] vector3 = ArrayN.addVectors( vector1, vector2 );

        for ( int num : vector3 )
        {
            System.out.print( num );
        }
        System.out.println();

        System.out.println();

        //Matrix
        int[][] matrix1 = {{0, 1, 2, 3, 4}, {4, 3, 2, 1, 0}};
        int[][] matrix2 = {{4, 3, 2, 1, 0}, {0, 1, 2, 3, 4}};

        int[][] matrix3 = ArrayN.addMatrices( matrix1, matrix2 );

        for ( int[] vector : matrix3 )
        {
            for ( int num : vector )
            {
                System.out.print( num );
            }
            System.out.println();
        }

        System.out.println();

        //N-Array

        System.out.println( Arrays.deepToString( (Object[])ArrayN.addArraysN( (Object)matrix1, (Object)matrix2, 2, 5 ) ) );

    }

    public static int[] addVectors( int[] a, int[] b )
    {
        int[] c = new int[a.length];

        for ( int i = 0; i < a.length; i++ )
        {
            c[i] = a[i] + b[i];
        }

        return c;
    }

    public static int[][] addMatrices( int[][] a, int[][] b )
    {
        int[][] c = new int[a.length][a[0].length];

        for ( int i = 0; i < a.length; i++ )
        {
            c[i] = ArrayN.addVectors( a[i], b[i] );
        }

        return c;
    }

    public static Object addArraysN( Object arrayN1, Object arrayN2, int dimension, int innerlength )
    {
        if ( dimension == 0 )
        {
            return (int)arrayN1 + (int)arrayN2;
        }
        else
        {
            int[] dimensions = new int[dimension];
            for ( int i = 0; i < dimension; i++ )
            {
                dimensions[i] = innerlength;
            }
            Object arrayN3 = Array.newInstance( Array.class, dimensions );
            for ( int i = 0; i < Array.getLength( arrayN1 ); i++ )
            {
                Array.set( arrayN3, i, ArrayN.addArraysN( Array.get( arrayN1, i ), Array.get( arrayN2, i ), dimension-1, innerlength ) );
            }

            return arrayN3;
        }
    }
}

输出：

44444

44444
44444

Exception in thread "main" java.lang.IllegalArgumentException: array element type mismatch
    at java.lang.reflect.Array.set(Native Method)
    at ArrayN.addArraysN(ArrayN.java:85)
    at ArrayN.addArraysN(ArrayN.java:85)
    at ArrayN.main(ArrayN.java:41)

附录2

我发现了错误。 它是以下行：

Object arrayN3 = Array.newInstance( Array.class, dimensions );

我不得不更换Array.class与int.class 。 更正后的行应为：

Object arrayN3 = Array.newInstance( int.class, dimensions );

现在我意识到代码有另一个问题：
由于innerlength参数，多维数组中的每个数组都必须具有相同的大小。 如果数组较短，则其他值变为零：

44444

44444
44444

[[4, 4, 4, 4, 4], [4, 4, 4, 4, 4], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]

所以我首先使matrix1和matrix2更长一些：

//Matrix
int[][] matrix1 = {{0, 1, 2, 3, 4}, {4, 3, 2, 1, 0}, {0, 1, 2, 3, 4}, {4, 3, 2, 1, 0}, {0, 1, 2, 3, 4}};
int[][] matrix2 = {{4, 3, 2, 1, 0}, {0, 1, 2, 3, 4}, {4, 3, 2, 1, 0}, {0, 1, 2, 3, 4}, {4, 3, 2, 1, 0}};

但这不是一个好的解决方案。
Nikoloz写了一个方法来找出数组的维数。 使用它和另一个方法arrayToString( Object )我现在编写了我的最终代码：

import java.util.Arrays;
import java.lang.reflect.Array;
import java.util.List;
import java.util.ArrayList;

public class ArrayN
{
    public static void main( String[] args )
    {
        int[][] matrix1 = {{0, 1, 2, 3, 4}, {4, 3, 2, 1, 0}};
        int[][] matrix2 = {{4, 3, 2, 1, 0}, {0, 1, 2, 3, 4}};

        System.out.println( ArrayN.arrayToString( ArrayN.addArraysN( matrix1, matrix2 ) ) );

    }

    public static Object addArraysN( Object arrayN1, Object arrayN2 )
    {
        ArrayList<Integer> dimensions = new ArrayList<Integer>();
        ArrayN.getDimensions( arrayN1, dimensions );
        int[] dims = new int[dimensions.size()];
        for ( int i = 0; i < dims.length; i++ )
        {
            dims[i] = dimensions.get( i );
        }

        if ( dims.length == 0 )
        {
            return (int)arrayN1 + (int)arrayN2;
        }
        else
        {
            Object arrayN3 = Array.newInstance( int.class, dims );
            for ( int i = 0; i < Array.getLength( arrayN1 ); i++ )
            {
                Array.set( arrayN3, i, ArrayN.addArraysN( Array.get( arrayN1, i ), Array.get( arrayN2, i ) ) );
            }

            return arrayN3;
        }
    }

    public static void getDimensions( Object array, List<Integer> dimensions )
    {
        if ( array != null && array.getClass().isArray() )
        {
            dimensions.add( Array.getLength( array ) );
            if ( Array.getLength( array ) > 0)
            {
                ArrayN.getDimensions( Array.get( array, 0 ), dimensions );
            }
        }
    }

    public static String arrayToString( Object arr )
    {
        if ( arr instanceof byte[] )
            return Arrays.toString( (byte[])arr );
        else if ( arr instanceof short[] )
            return Arrays.toString( (short[])arr );
        else if ( arr instanceof int[] )
            return Arrays.toString( (int[])arr );
        else if ( arr instanceof long[] )
            return Arrays.toString( (long[])arr );
        else if ( arr instanceof float[] )
            return Arrays.toString( (float[])arr );
        else if ( arr instanceof double[] )
            return Arrays.toString( (double[])arr );
        else if ( arr instanceof char[] )
            return Arrays.toString( (char[])arr );
        else if ( arr instanceof boolean[] )
            return Arrays.toString( (boolean[])arr );
        else
            return Arrays.deepToString( (Object[])arr );
    }
}

另一种可能性是将维度1作为基本情况：

public static Object addArraysN( Object arrayN1, Object arrayN2 )
{
    ArrayList<Integer> dimensions = new ArrayList<Integer>();
    ArrayN.getDimensions( arrayN1, dimensions );
    int[] dims = new int[dimensions.size()];
    for ( int i = 0; i < dims.length; i++ )
    {
        dims[i] = dimensions.get( i );
    }
    if ( dims.length == 1 )
    {
        Object arrayN3 = Array.newInstance( int.class, dims );
        for ( int i = 0; i < Array.getLength( arrayN1 ); i++ )
        {
            int sum = ((int[])arrayN1)[i] + ((int[])arrayN2)[i];
            Array.set( arrayN3, i, sum );
        }
        return arrayN3;
    }
    else
    {
        Object arrayN3 = Array.newInstance( int.class, dims );
        for ( int i = 0; i < Array.getLength( arrayN1 ); i++ )
        {
            Array.set( arrayN3, i, (int[])ArrayN.addArraysN( Array.get( arrayN1, i ), Array.get( arrayN2, i ) ) );
        }

        return arrayN3;
    }
}

相关问题

如何在Java中对数组求和
是否可以在Java中动态构建多维数组？
通过反射迭代数组
Java Reflection - 获取数组对象的大小
在运行时期间使用Java创建n维数组
在Java中初始化多维数组
找到二维数组java的总和
添加矩阵Java
Java矩阵数组

Answer 1

这是完整而简单的解决方案。 您可以将任何维数组传递给copyArray方法。

package com.azry.test;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;

public class MultiDimArray {

    public Object copyArray(Object srcArray1, Object srcArray2) {

        ArrayList<Integer> dimensions = new ArrayList<Integer>();
        getDimensions(srcArray1, dimensions);
        int[] dims = new int[dimensions.size()];
        for (int i = 0; i < dims.length; i++) {
            dims[i] = dimensions.get(i);
        }

        Object dstArray = Array.newInstance(int.class, dims);
        copyArray(srcArray1, srcArray2, dstArray);
        return dstArray;
    }

    public void copyArray(Object srcArray1, Object srcArray2, Object dstArray) {
        if (srcArray1 != null && srcArray1.getClass().isArray()) {
            if (srcArray1 instanceof int[]) {
                int[] s1 = (int[])srcArray1;
                int[] s2 = (int[])srcArray2;
                int[] d = (int[])dstArray;
                for (int i = 0; i < s1.length; i++) {
                    d[i] = s1[i] + s2[i];
                }
            }
            for (int i = 0; i < Array.getLength(srcArray1); i++) {
                copyArray(Array.get(srcArray1, i), Array.get(srcArray2, i), Array.get(dstArray, i));
            }
        }
    }

    public void getDimensions(Object array, List<Integer> dimensions) {
        if (array != null && array.getClass().isArray()) {
            dimensions.add(Array.getLength(array));
            if (Array.getLength(array) > 0) {
                getDimensions(Array.get(array, 0), dimensions);
            }
        }
    }

    public static void main(String[] args) {

        int[][][] srcArray1 = new int[2][3][4];
        for (int i = 0; i < srcArray1.length; i++) {
            for (int j = 0; j < srcArray1[i].length; j++) {
                for (int k = 0; k < srcArray1[i][j].length; k++) {
                    srcArray1[i][j][k] = 2;
                }
            }
        }

        int[][][] srcArray2 = new int[2][3][4];
        for (int i = 0; i < srcArray2.length; i++) {
            for (int j = 0; j < srcArray2[i].length; j++) {
                for (int k = 0; k < srcArray2[i][j].length; k++) {
                    srcArray2[i][j][k] = 3;
                }
            }
        }

        int[][][] dstArray = (int[][][])new MultiDimArray().copyArray(srcArray1, srcArray2);

        for (int i = 0; i < dstArray.length; i++) {
            for (int j = 0; j < dstArray[i].length; j++) {
                for (int k = 0; k < dstArray[i][j].length; k++) {
                    System.out.println("[" + i + "," + j + "," + k + "] = " + dstArray[i][j][k]);
                }
            }
        }
    }
}

Answer 2

问题是您不能像当前那样处理数组：您在addVectorsN(...)中接收的Object vectorN1实际上是(Object)matrice1 ，因此int[][] 。 但是，你可以像(int)vectorN1一样访问它，这是错误的，因为它实际上是一个数组，而不是一个int。 所以，您应该像这样访问vectorN1： int i = ...; vectorN1[i]; int i = ...; vectorN1[i]; 然后我将vectorN1保持为int[][]而不是将其转换为Object 。 我也会对vectorN2做同样的事情。

编辑：

我会改变

addVectorsN( (Object)matrice1, (Object)matrice2, 2, 5 ) )

addVectorsN( matrice1, matrice2, 2, 5 ) )

你正在访问它像(int)vectorN1 in

public static Object addVectorsN( Object vectorN1, Object vectorN2, 
    int dimension, int innerlength )
{
    if ( dimension == 0 )
    {
        return (int)vectorN1 + (int)vectorN2; (...) 

我将改为：

public static Object addVectorsN(int[][] vectorN1, int[][] vectorN2, 
    int dimension, int innerlength )

EDIT2：

也许你需要这样的东西：

    if (vectorN1.length == 1 && vectorN2.length == 1)
    {
        if (vectorN1[0].length == 1  && vectorN2[0].length == 1)
        {
            return vectorN1[0][0] + vectorN2[0][0];
        }
    }

Answer 3

这将完全按照你的要求做：

public static Object sumArbitraryDimensions(Object arrayOne, Object arrayTwo) {
    if (!arrayOne.getClass().equals(arrayTwo.getClass()) ||
            !arrayOne.getClass().isArray()) {
        throw new IllegalArgumentException("not an array");
    }

    int len = Array.getLength(arrayOne);
    if (len != Array.getLength(arrayTwo)) {
        throw new IllegalArgumentException("incomparable length");
    }

    Object sum;

    if (arrayOne instanceof Object[]) {
        sum = new Object[len];

        for (int i = 0; i < len; i++) {
            ((Object[])sum)[i] = sumArbitraryDimensions(
                    Array.get(arrayOne, i), Array.get(arrayTwo, i));
        }

    } else if (arrayOne instanceof byte[]) {
        sum = new byte[len];

        for (int i = 0; i < len; i++) {
            ((byte[])sum)[i] = (byte)(((byte[])arrayOne)[i] + ((byte[])arrayTwo)[i]);
        }

    } else if (arrayOne instanceof short[]) {
        sum = new short[len];

        for (int i = 0; i < len; i++) {
            ((short[])sum)[i] = (short)(((short[])arrayOne)[i] + ((short[])arrayTwo)[i]);
        }

    } else if (arrayOne instanceof int[]) {
        sum = new int[len];

        for (int i = 0; i < len; i++) {
            ((int[])sum)[i] = ((int[])arrayOne)[i] + ((int[])arrayTwo)[i];
        }

    } else if (arrayOne instanceof long[]) {
        sum = new long[len];

        for (int i = 0; i < len; i++) {
            ((long[])sum)[i] = ((long[])arrayOne)[i] + ((long[])arrayTwo)[i];
        }

    } else if (arrayOne instanceof float[]) {
        sum = new float[len];

        for (int i = 0; i < len; i++) {
            ((float[])sum)[i] = ((float[])arrayOne)[i] + ((float[])arrayTwo)[i];
        }

    } else if (arrayOne instanceof double[]) {
        sum = new double[len];

        for (int i = 0; i < len; i++) {
            ((double[])sum)[i] = ((double[])arrayOne)[i] + ((double[])arrayTwo)[i];
        }

    } else {
        throw new IllegalArgumentException("cannot sum, non-numerical");
    }

    return sum;
}

或者略显冗长但不那么简洁：

public static Object sumArbitraryDimensions(Object arrayOne, Object arrayTwo) {
    // exceptions unchecked

    int len = Array.getLength(arrayOne);

    if (arrayOne instanceof Object[]) {
        Object[] sum = new Object[len];

        for (int i = 0; i < len; i++) {
            ((Object[])sum)[i] = sumArbitraryDimensions(
                    Array.get(arrayOne, i), Array.get(arrayTwo, i));
        }

        return sum;

    } else {
        Double[] sum = new Double[len];

        // works for any numerical primitive type because
        // getDouble will perform a widening conversion
        for (int i = 0; i < len; i++) {
            sum[i] = Array.getDouble(arrayOne, i) + Array.getDouble(arrayTwo, i);
        }

        return sum;
    }
}

或者，如果您真的想要达到可能的元素级别：

public static Object sumArbitraryDimensions(Object objectOne, Object objectTwo) {
    if (!arrayOne.getClass().equals(arrayTwo.getClass())) {
        throw new IllegalArgumentException("incomparable types");
    }

    // reflection cannot retrieve primitive types
    // here the returned arrays will be boxed

    if (objectOne.getClass().isArray()) {
        int len = Array.getLength(objectOne);

        if (len != Array.getLength(objectTwo)) {
            throw new IllegalArgumentException("incomparable lengths");
        }

        Object[] sum = new Object[len];

        for (int i = 0; i < len; i++) {
            sum[i] = sumArbitraryDimensions(
                    Array.get(arrayOne, i), Array.get(arrayTwo, i));
        }

        return sum;

    } else if (objectOne instanceof Byte) {
        return (byte)((Byte)objectOne + (Byte)objectTwo));

    } else if (objectOne instanceof Short) {
        return (short)((Short)objectOne + (Short)objectTwo));

    } else if (objectOne instanceof Integer) {
        return (Integer)objectOne + (Integer)objectTwo);

    } else if (objectOne instanceof Long) {
        return (Long)objectOne + (Long)objectTwo);

    } else if (objectOne instanceof Float) {
        return (Float)objectOne + (Float)objectTwo);

    } else if (objectOne instanceof Double) {
        return (Double)objectOne + (Double)objectTwo);

    } else {
        throw new IllegalArgumentException("cannot sum, non-numerical");
    }
}

由于所有检查，所有这些与常规处理相比将非常缓慢。 我个人建议不要以任何形式或形式这样做。 我没有看到它的用途。 只需编写最多N维的重载方法：

public static int[] sumArrays(int[] arrayOne, int[] arrayTwo) {
    assert arrayOne != null && arrayTwo != null && arrayOne.length == arrayTwo.length;

    int[] sum = new int[Math.min(arrayOne.length, arrayTwo.length)];

    for (int i = 0; i < sum.length; i++) {
        sum[i] = arrayOne[i] + arrayTwo[i];
    }
    return sum;
}

public static int[][] sumArrays(int[][] arrayOne, int[][] arrayTwo) {
    assert arrayOne != null && arrayTwo != null && arrayOne.length == arrayTwo.length;

    int[][] sum = new int[Math.min(arrayOne.length, arrayTwo.length)][];

    for (int i = 0, k; i < sum.length; i++) {
        assert arrayOne[i] != null && arrayTwo[i] != null && arrayOne[i].length == arrayTwo[i].length;

        sum[i] = new int[Math.min(arrayOne[i].length, arrayTwo[i].length)];

        for (k = 0; k < sum[i].length; k++) {
            sum[i][k] = arrayOne[i][k] + arrayTwo[i][k];
        }
    }
    return sum;
}

public static int[][][] sumArrays(int[][][] arrayOne, int[][][] arrayTwo) {
    assert arrayOne != null && arrayTwo != null && arrayOne.length == arrayTwo.length;

    int[][][] sum = new int[Math.min(arrayOne.length, arrayTwo.length)][][];

    for (int i = 0, k, h; i < sum.length; i++) {
        assert arrayOne[i] != null && arrayTwo[i] != null && arrayOne[i].length == arrayTwo[i].length;

        sum[i] = new int[Math.min(arrayOne[i].length, arrayTwo[i].length)][];

        for (k = 0; k < sum[i].length; k++) {
            assert arrayOne[i][k] != null && arrayTwo[i][k] != null && arrayOne[i][k].length == arrayTwo[i][k].length;

            sum[i][k] = new int[Math.min(arrayOne[i][k].length, arrayTwo[i][k].length)];

            for (h = 0; h < sum[i][k].length; h++) {
                sum[i][k][h] = arrayOne[i][k][h] + arrayTwo[i][k][h];
            }
        }
    }
    return sum;
}