Could I rewrite this function with single loop?

JavaScript
1

I have a suspicion that function like below can be written with single loop(maybe not), but can’t figure out, how to achieve that.

//TASK function must return 2-dimensional array, 
//representing NxN grid(matrix), with coordinates(indexes) for each element

//WHY? some visualization seems to be helpful when working on 
//Project Euler 11 problem

const generateQuadraticTestGrid = (size) => {
  
  let testGrid = [];
  
  for (let i = 0; i < size; i++) {
  testGrid.push([])
  for (let j = 0; j < size; j++) {
    testGrid[i].push(String(i) + ',' + String(j));
  }
  
  
  }
  
  return testGrid;
  
}


console.log(generateQuadraticTestGrid(6))

/*
Output:

[
  [ '0,0', '0,1', '0,2', '0,3', '0,4', '0,5' ],
  [ '1,0', '1,1', '1,2', '1,3', '1,4', '1,5' ],
  [ '2,0', '2,1', '2,2', '2,3', '2,4', '2,5' ],
  [ '3,0', '3,1', '3,2', '3,3', '3,4', '3,5' ],
  [ '4,0', '4,1', '4,2', '4,3', '4,4', '4,5' ],
  [ '5,0', '5,1', '5,2', '5,3', '5,4', '5,5' ]
]
*/
2

Can you elaborate a little more on your suspicions? Don’t worry so much about creating a multi-dimensional array right now. How would you dynamically create a single array and add n elements to it without using some form of iteration?

2 Likes
3

That’s a question I needed to hear I guess.

There was discussion about some problem related to 2-dimensional arrays. At some point it became clear, that there single loop could be used instead of nested loops.

I guess I am just overthinking stuff after that, making bad analogies. My problem here is to generate array, not to access elements in existing array.

4

I don’t think you are using the word ‘quadratic’ correctly here.

Using push is a particularly slow way to build up an array in Javascript, if you are making a big array.

5

Yeah, that’s the case probably. What would be appropriate word in English?

6

If you are making a 2D array, I’d just call it a 2D array.

7

Well, if 2D array has size NxN(4x4 for example), and it is filled with numbers:

it’s basically matrix,right? If matrix has NxN size, how do I call it? square maybe?
quadratic it was just similar to my native language word for such thing

8

It’s just a 2D array in programming. You could call it a square matrix fr math applications, but it certainly is not quadratic. ‘Quadratic’ has a specific mathematical meaning.

9

Thanks, I think terminology became clear for me.
What about alternatives for push?
I am reading this right now:

More than one option there… Discussion is about how to create array of numbers from 1 to 10

var num = 10,
  dynar = [...Array(num)].map((_,i) => ++i+"");
console.log(dynar);

Array.apply(null, new Array(10)).map(function(el, i) {return ++i + ""})

Also there is Array.from()

10

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