squareUp challenge

Given n>=0, create an array length n*n with the following pattern, shown here for n=3 : {0, 0, 1,    0, 2, 1,    3, 2, 1} (spaces added to show the 3 groups).

squareUp(3) → [0, 0, 1, 0, 2, 1, 3, 2, 1]
squareUp(2) → [0, 1, 2, 1]
squareUp(4) → [0, 0, 0, 1, 0, 0, 2, 1, 0, 3, 2, 1, 4, 3, 2, 1]

i have not understood the challenge description.

How below are expected outputs?

squareUp(3) → [0, 0, 1, 0, 2, 1, 3, 2, 1]
squareUp(2) → [0, 1, 2, 1]
squareUp(4) → [0, 0, 0, 1, 0, 0, 2, 1, 0, 3, 2, 1, 4, 3, 2, 1]

As a warm-up, how would you make an array that contained the integers from  0  to  n² -1 ??

You shift the numbers into the array from the right in groups. Example for 5:

0,0,0,0,1
0,0,0,2,1
0,0,3,2,1
0,4,3,2,1
5,4,3,2,1

this is clear now. let me think on it now

OK ;)

looks like i may need two loops for this also

You shift the numbers into the array from the right in groups. Example for 5:

how to represent this push in code?

not yet

"Wow" indeed.
Do you realize that printing the array in an n x n grid rather than an n² x 1 string is an enormous hint?

Do you realize that printing the array in an n x n grid rather than an n² x 1 is an enormous hint?

not able to realize. I just see some additional spaces.


0,0,0,0,1
0,0,0,2,1
0,0,3,2,1
0,4,3,2,1
5,4,3,2,1

compared to above below?

0,0,0,0,     1
0,0,0,     2,1
0,0,     3,2,1
0,     4,3,2,1
     5,4,3,2,1

There are two ways to build an array with n² elements:

  for i= 0 to n² by 1

  for i= 0 to n by 1
     for j= 0 to n by 1

The second method might be useful if you can see the pattern in the grid.

 for i= 0 to n by 1
     for j= 0 to n by 1

The second method might be useful if you can see the pattern in the grid.

which grid? what is grid?
you mean below?

0,0,0,0,     1
0,0,0,     2,1
0,0,     3,2,1
0,     4,3,2,1
     5,4,3,2,1

to me above looks lik e2 D array not 1 Dimensional?

Yes, you have to build a 1-D array.
Gerwin Jansen gave you an enormous hint by drawing it as an nxn matrix so you can see the pattern.

The grid is the 2D array we've shown you to help understand the question. Your function should return a single string of numbers.

squareUp(2) → [0, 1, 2, 1]
0,1
2,1

squareUp(1) → [0, 1]
0
1

I am sure this is not correct.  There can only be n*n elements.

squareUp(1) → [0, 1]

0
1

The answer is probably [1], but it may depend on your implementation.

And squareUp(0) → [ ]  because it must have 0*0 elements.

@d-glitch - You are correct, 1*1=1 :D

squareUp(1) would have to result in [1] - independent of the implementation.

Each group is n wide starting with a 1 on the right side, this would result in [1]

public int[] squareUp(int n) {
  
	    int[] finalRes = new int[n * n];
	    int indx = 0;
	 
	    for (int i = 1; i <= n; i++) {
	        for (int k = 1; k <= n - i; k++)
	        	finalRes[indx++] = 0;
	        for (int j = i; j > 0; j--) 
	        	finalRes[indx++] = j;
	    }
	    return finalRes;
	
}

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above passes all tests.

Expected      Run            
squareUp(3) → [0, 0, 1, 0, 2, 1, 3, 2, 1]      [0, 0, 1, 0, 2, 1, 3, 2, 1]      OK      
squareUp(2) → [0, 1, 2, 1]      [0, 1, 2, 1]      OK      
squareUp(4) → [0, 0, 0, 1, 0, 0, 2, 1, 0, 3, 2, 1, 4, 3, 2, 1]      [0, 0, 0, 1, 0, 0, 2, 1, 0, 3, 2, 1, 4, 3, 2, 1]      OK      
squareUp(1) → [1]      [1]      OK      
squareUp(0) → []      []      OK      
squareUp(6) → [0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 2, 1, 0, 0, 0, 3, 2, 1, 0, 0, 4, 3, 2, 1, 0, 5, 4, 3, 2, 1, 6, 5, 4, 3, 2, 1]      [0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 2, 1, 0, 0, 0, 3, 2, 1, 0, 0, 4, 3, 2, 1, 0, 5, 4, 3, 2, 1, 6, 5, 4, 3, 2, 1]      OK      

All Correct

any improvements/refinements/alternate approaches?

It is passing all tests, code looks OK to me.