在Java中添加两个n维数组
添加 vector
Java 中的两个一维数组/vector 可以这样相加:
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;
}
添加矩阵
Java中两个二维数组/矩阵可以这样相加:
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的大小相同,以避免 arrayOutOfBoundsException
。
添加数组N
应该有一种方法可以使用递归将两个未知维度的数组相加。
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 )
。
我从以下伪代码开始:
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
}
}
可以使用来自 java.lang.reflect.Array 的 newInstance
方法创建新数组.
循环可以像这样成为可能:
for ( int i = 0; i < ((int[])arr1).length; i++ )
sum = addArraysN( ((int[])arr1)[i], ((int[])arr2)[i] );
问题
但是我偶然发现了很多运行时错误和其他问题。关于如何实现此 addArrayN
方法,有人有想法甚至解决方案吗?
应该也可以使用 ArrayList
或任何其他类,但我主要对如何使用数组执行此操作感兴趣...(尽管如此,如果有人知道,请发帖!)
提前致谢
附录1
我的原始代码:
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。这是下面一行:
Object arrayN3 = Array.newInstance( Array.class, dimensions );
我必须用 int.class
替换 Array.class
。更正后的行应该是:
Object arrayN3 = Array.newInstance( int.class, dimensions );
现在我意识到代码的另一个问题:
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。如果数组更短,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]]
所以我首先让matrix1
和matrix2
长一点:
//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度。使用它和另一种方法 arrayToString( Object )
我现在写的最终代码是:
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
How to sum arrays in Java
Is it possible to dynamically build a multi-dimensional array in Java?
Iterating over arrays by reflection
Java Reflection - Get size of array object
Creating an n-dimension Array in Java during runtime
Initialising a multidimensional array in Java
finding sum of two dimensional array java
Adding matrices Java
Java Matrices Arrays
最佳答案
这是完整而简单的解决方案。您可以将任何维度数组传递给 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]);
}
}
}
}
}
关于java - Java中如何获取两个n维数组的和?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20020599/