在JAVA中将1d数组转换为2d数组

Question

I am trying to input values from a 1d array into a 2d array in java.

This is what I have so far:

int[] input2 = {
    0, 1, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0
};
int[][] arr = new arr[3][4];

for (int i = 0; i < arr.length; i++) {
    for (int j = 0; j < arr[i].length; j++) {
        System.out.println("index" + ((i * arr.length) + j));
        arr[i][j] = input2[(i * arr.length) + j];
        //System.out.print("  " + arr[i][j]);

    }
    //System.out.println();
 }

But what it outputs is:

index0
index1
index2
index3
index3
index4
index5
index6
index6
index7
index8
index9

which means that I am getting the indexes wrong from 1d array. Where did I go wrong ?

Answer 1

Your mistake is that in each step you multiply by the number of rows rather than the number of columns .

If you want to get to the first element of the second row, you have to skip all the elements of the first row first. That would be 1 * arr[0].length . So your method may work in an X by X array, but not in an X by Y array.

Answer 2

It could well be filling in 2 dimensions, but ((i*arr.length) + j) is probably just adding the values. I would add '+ ", "' in the middle of it to see what is actually getting output.

Answer 3

在您的循环中尝试-

((i*arr[0].length) + j) 

Answer 4

You should change your index formula from :

(i*arr.length) + j

to

(i*arr[i].length) + j

Answer 5

you can try this:

    int count = 0;
    for(int i=0; i< arr.length; i++)
     {
         for(int j=0; j<arr[i].length; j++)
         {
             //System.out.println("index" + ((i*arr.length) + j) );
             arr[i][j] = input2[count++];
             System.out.print("  " + arr[i][j]);

         }
    System.out.println();
     }

Answer 6

Try

int[] input2 = {0,1,0,0,0,1,1,0,1,0,1,0};
 int[][] arr = new arr[3][4];

for(int i=0; i< arr.length; i++)
         {
             for(int j=0; j<arr[i].length; j++)
             {
                 System.out.println("index" + ((i*arr[i].length) + j) );
                 arr[i][j] = input2[(i*(arr[i].length)) + j];
                 //System.out.print("  " + arr[i][j]);

             }
        //System.out.println();
         }

(Replaced ((i*arr.length) + j) with ((i*arr[i].length) + j)