[英]How to convert a 1d array to 2d array?
Say, I have a 1d array with 30 elements:说,我有一个包含 30 个元素的一维数组:
array1d[0] = 1
array1d[1] = 2
array1d[2] = 3
.
.
.
array1[29] = 30
How to convert the 1d array to 2d array?如何将一维数组转换为二维数组?
Say 10x3?说 10x3?
array2d[0][0] = 1 array2d[0][1] =2 array2d[0][2] =3
.
.
.
array2d[9][0] = 28 array2d[9][1] =29 array2d[9][2] =30
Should I use a for loop?我应该使用for循环吗?
But I cannot work it out.但我无法解决。
int array2d[][] = new int[10][3];
for(int i=0; i<10;i++)
for(int j=0;j<3;j++)
array2d[i][j] = array1d[(j*10) + i];
Without writing any code for you...无需为您编写任何代码...
So it will look something like...所以它看起来像......
I'm being intentionally vague, seeing as this is homework.我故意含糊其辞,因为这是家庭作业。 Try posting some code so we can see where you get stuck.尝试发布一些代码,以便我们了解您遇到的问题。
Here a generic function to convert from 1D -> 2D array:这里有一个从 1D -> 2D 数组转换的通用函数:
public int[][] monoToBidi( final int[] array, final int rows, final int cols ) {
if (array.length != (rows*cols))
throw new IllegalArgumentException("Invalid array length");
int[][] bidi = new int[rows][cols];
for ( int i = 0; i < rows; i++ )
System.arraycopy(array, (i*cols), bidi[i], 0, cols);
return bidi;
}
If you want to do the contrary (2D -> 1D), here the function:如果你想做相反的事情(2D -> 1D),这里的功能:
public int[] bidiToMono( final int[][] array ) {
int rows = array.length, cols = array[0].length;
int[] mono = new int[(rows*cols)];
for ( int i = 0; i < rows; i++ )
System.arraycopy(array[i], 0, mono, (i*cols), cols);
return mono;
}
public class Test{
public static void main(String[] argv)
{
int x,y;
for(int num =0; num<81;num++)
{
if((num % 9)>0)
{
x = num/9;
y = num%9;
}else
{
x = num/9;
y = 0;
}
System.out.println("num ["+num+"]---["+x+","+y+"]");
}
}
}
/* Replace 9 by the size of single row of your 2D array */
You often will find the same problem: how to manipulate 2D array as 1D array.你经常会发现同样的问题:如何将二维数组作为一维数组进行操作。 I wrote a generic class Grid, that lets access objects by index or by (x,y) .我编写了一个通用类 Grid,它允许通过索引或(x,y)访问对象。
See the following class and understand the idea behind it.请参阅以下课程并了解其背后的想法。 :) :)
You could use the following class for data manipulation as 2D array or 1D array.您可以使用以下类作为二维数组或一维数组进行数据操作。 Here is the code for that I wrote and use.这是我编写和使用的代码。
/**
* Grid represents a 2 dimensional grid.
*
* @param <E> the type of elements in this grid
*/
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
public class Grid<E>
{
private int size ;
private int width ;
private int height ;
private List<E> elements;
public int getCapacity()
{
return getWidth() * getHeight();
}
/**
* @return number of elements in grid. Null is also an element.
*/
public int getSize()
{
return getElements().size();
}
/**
* @param sideSize size of the grid side
*/
public Grid(int sideSize)
{
this(sideSize,sideSize);
}
/**
* @param width of the grid
* @param height of the grid
*/
public Grid(int width, int height)
{
this.width = width ;
this.height = height;
this.elements = new ArrayList<E>(
Collections.nCopies(width*height, (E)null));
}
public int getHeight()
{
return height;
}
public int getWidth()
{
return width;
}
/**
* @return all elements of the grid
*/
public List<E> getElements()
{
return elements;
}
/**
* @return iterator for a grid
*/
public Iterator<E> iterator()
{
return getElements().iterator();
}
/**
* Returns the element at position (x,y).
*
* @return the element at position (x,y)
*/
public E get(int x, int y)
{
return getElements().get(
idx(x,y));
}
/**
* Returns the element at index idx.
*
* @return the element at given index
*/
public E get(int idx)
{
return getElements().get(idx);
}
/**
* Puts an element to the position idx
*
* @param element to be added
*
* @param x position x to add element to
*
* @param y position y to add element to
*/
public void put(int x, int y, E element)
{
put(idx(x,y), element);
}
/**
* Puts an element to the position idx
*
* @param element to be added
*
* @param idx to add element at
*/
public void put(int idx, E element)
{
getElements().add(idx, element);
}
/**
* Returns the x coordinate from the index.
*
* @return x coordinate of the index
*/
public int x(int idx)
{
return idx % getHeight();
}
/**
* Returns the y coordinate from the index.
*
* @return y coordinate of the index
*/
public int y(int idx)
{
return (idx - idx % getHeight()) / getHeight();
}
/**
* Returns index of element at (x,y).
*
* @return index of the coordinates
*/
public int idx(int x, int y)
{
return y*getHeight() + x;
}
}
Here is how to use the class (see a test example):以下是该类的使用方法(请参阅测试示例):
public class TestGrid
{
public static final int SIZE = 10;
public static final Integer el1 = new Integer(2);
public static final Integer el2 = new Integer(3);
public static final Integer el3 = new Integer(3);
public static void main(String[] args)
{
Grid<Integer> grid = new Grid<>(SIZE);
assert grid.getCapacity() == SIZE*SIZE ;
assert grid.idx(0,0) == 0 ;
assert grid.idx(1,0) == 1 ;
assert grid.idx(0,1) == 10;
assert grid.idx(6,1) == 16;
assert grid.idx(9,9) == 99;
grid.put(1, el1);
assert grid.get(1) == el1 : grid.get(1);
grid.put(0, 1, el2);
assert grid.get(0,1) != el1 && el1 != el2 && grid.get(0,1) == el2;
grid.put(15, el3);
assert grid.get(5,1) == el3;
}
}
int[] oneDArray = new int[arr.length*arr.length];
//Flatten 2D array to 1D array...
int s = 0;
for(int i = 0; i < arr.length; i ++)
for(int j = 0; j < arr.length; j ++){
oneDArray[s] = arr[i][j];
s++;
}
package com.vikrant;
import java.util.Arrays;
public class TwoD {
public static void main(String args[])
{
int a[][]=new int[4][3];
int d[]={10,20,30,40,50,60,70,80,90,100,110,120};
int count=0;
for(int i=0;i<4;i++)
{
for(int j=0;j<3;j++)
{
if(count==d.length) break;
a[i][j]=d[count];
count++;
}}
int j=0;
for (int i = 0; i<4;i++)
{
for(j=0;j<3;j++)
System.out.println(a[i][j]);
}
}}
THIS DOES THE WORK这行得通
This is just a pseudo code.这只是一个伪代码。 ROWS represent the length of the 2d array, and COLUMNS represent the length of the 1st element in the array ROWS 表示二维数组的长度,COLUMNS 表示数组中第一个元素的长度
for(i=0; i<ROWS; i++)
for(j=0; j<COLUMNS; j++)
array2d[i][j] = array1d[ (i*COLUMNS) + j];
您不能将一维数组“转换”为二维数组,但声明数组时可以是多维数组。
int myArray2d[][] = new int[10][3]
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