How can I find the two positions with the two highest numbers in a multidimensional array?

Question

I'm working in a JavaScript project where in this case I am trying to get the two arrays with the biggest value in position 2.

[-20.172, 35.251, 0],
[-16.368, 21.792, 26.81],
[-29.311, 18.393, 0],
[14.54, 15.23, 0],
[-1.61, 12.91, 27.692],
[0, 0, 0]

the intended answer should be like this:

[-16.368, 21.792, 26.81],
[-1.61, 12.91, 27.692]

I can't sort by the ones that have a zero and the ones who doesn't have it, some other cases in the project I'm working could possibly have different numbers on the position 2.

any suggestions?

what do you mean with zeros? what have you tried? btw, why not sorting? — Nina Scholz, Apr 06 '22 at 19:06
Use `sort()` with a comparison function that compares index 2 of the elements. — Barmar, Apr 06 '22 at 19:06
@Barmar, there's not a chance in .... that he will be able to figure out the compare function — DCR, Apr 06 '22 at 19:34
@DCR OK, I closed it as a duplicate of a question that shows how to do that. — Barmar, Apr 06 '22 at 19:35

score 1 · Accepted Answer · answered Apr 06 '22 at 19:39

Using Array#reduce:

const arr = [
  [-20.172, 35.251, 0],
  [-16.368, 21.792, 26.81],
  [-29.311, 18.393, 0],
  [14.54, 15.23, 0],
  [-1.61, 12.91, 27.692],
  [0, 0, 0]
];

const [max1Index, max2Index] = arr.reduce(([max1Index, max2Index], { 2: num }, index) => {
  const max1 = arr[max1Index][2], max2 = arr[max2Index][2];
  return num > max1
    ? [index, max1Index]
    : num > max2
      ? [max1Index, index]
      : [max1Index, max2Index];
}, [0, 0]);

console.log(arr[max1Index], arr[max2Index]);

That's what I was looking for! thank you very much!, I knew it was with reduce but I didn't figured out the way to do it. — Tomas Emilio Alvarez Yunginger, Apr 06 '22 at 19:48

radarbob · Answer 2 · 2022-04-06T20:47:56.570

I can't sort by the ones that have a zero

Could it be the array is declared const?

Array.Sort

Array.Slice

sorts, in place, descending
returns an array of (copies of) first 2 elements

    var topTwo = function ( array_of_arrays ) {
      return array_of_arrays.sort((a, b) => b[2] - a[2])
                            .slice(0, 2) ;
    };

    var arr = [
      [-20.172, 35.251, 7],
      [-16.368, 21.792, 26.81],
      [-29.311, 18.393, 0],
      [14.54, 15.23, 0],
      [-1.61, 12.91, 27.692],
      [0, 0, -3]
    ];
    console.log( topTwo(arr) );

How can I find the two positions with the two highest numbers in a multidimensional array?

2 Answers2