how to transfer an array to two-d array in java

Question

i want to transfer an n elements array to a two-d array in java.

For example:

[1,2,3,4]

this array should be transferred to an two-d array

[[1, 2], [1, 3], [1, 4], [2, 3], [2, 4] [3,4]]

the first line of the two-d array is 1, 2.
the second line of the two- array is 1, 3.
the third line of the two-array is 1, 4.
the forth line of the two-array is 2, 3.
the fifth line of the two-array is 2, 4.
the last line is 3, 4

What have your tried?? And should the number of columns always be 2?? — Rohit Jain
– Rohit Jain, Commented Oct 11, 2012 at 4:35
@Justin.. Then how would you divide it when there are 10 elements in your array?? Please be clear with your specs.. — Rohit Jain
– Rohit Jain, Commented Oct 11, 2012 at 4:37
So, you are trying to create a two-dimensional array of all combinations of the elements in the first array? Specific details are necessary. — FThompson
– FThompson, Commented Oct 11, 2012 at 4:40
if there is a 6 element array. [1,2,3,4,5,6] the first line of the two-d array should be 1, 2 the second..................................1, 3 the third ..................................1, 4 the fifth...................................1, 5 the sixth...................................1, 6 the seventh.................................2, 3 the eight ..................................2, 4 so on so far — J.L
– J.L, Commented Oct 11, 2012 at 4:41
@Justin.. Well now that it is clear what you want.. It doesn't seem to be that tough. You should give it a try.. Write some Algorithm on Paper. and then see how it works.. — Rohit Jain
– Rohit Jain, Commented Oct 11, 2012 at 4:44

Raman · Accepted Answer · 2012-10-11 07:12:40Z

8

Without writing any code for you...

Think about how big your 2d array needs to be. Recognize that you'll need to loop over the contents of your source array to get each value into your destination array.

So it will look something like...

Create a 2d array of appropriate size. Use a for loop to loop over your 1d array. Inside that for loop, you'll need to figure out where each value in the 1d array should go in the 2d array. Try using the mod function against your counter variable to "wrap around" the indices of the 2d array. I'm being intentionally vague, seeing as this is homework. Try posting some code so we can see where you get stuck.

Or you can use that code:-

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];

edited Oct 11, 2012 at 7:12

Raman

2,0313 gold badges20 silver badges30 bronze badges

answered Oct 11, 2012 at 4:42

Tarun Gupta

1,2422 gold badges13 silver badges26 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Aubin Over a year ago

array2d[i][j] = array1d[(i*3) + j];

Uwe Keim · Accepted Answer · 2012-10-11 06:44:23Z

From Permutation and combination you can get the row length of the 2D array (ie. n!/r!*(n-r)!).

getLengthOfArray method does this.
calculatePermutation is a helper method to calculate permutaion.
transferToTwoDArray will give you the right answer.

public int[][] transferToTwoDArray(final int[] oneDArray)
{
    assert null != oneDArray;
    final int length = oneDArray.length;
    assert length > 2;

    final int newArrayLength = getLengthOfArray(length, 2);
    final int[][] newArray = new int[newArrayLength][2];

    int nextRowIndex = 0;
    for (int i = 0; i < length; i++)
    {
        int nextValue = i + 1;

        while (nextValue < length)
        {
            newArray[nextRowIndex][0] = oneDArray[i];
            newArray[nextRowIndex][1] = oneDArray[nextValue++];
            nextRowIndex++;
        }
    }
    return newArray;
}

/**
 * Calculate permutation.
 * 
 * @param length
 *            the length
 * @return the int
 */
private int calculatePermutation(final int length)
{
    if (length == 0)
    {
        return 1;
    }
    return length * calculatePermutation(length - 1);
}

/**
 * Gets the length of array.
 * 
 * @param length
 *            the length
 * @param arrayDimention
 *            the array dimention
 * @return the length of array
 */
private int getLengthOfArray(final int length, final int arrayDimention)
{
    return calculatePermutation(length)
            / ((calculatePermutation(arrayDimention)) * (calculatePermutation(length - arrayDimention)));
}

Cheers, Chand.

Collectives™ on Stack Overflow

how to transfer an array to two-d array in java

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related