--description--

Given an array of integers and a target number, find all pairs of elements in the array whose values add up to the target and return the sum of their indices.

For example, given [2, 3, 4, 6, 8] and 10, you will find two valid pairs:

• 2 and 8 (2 + 8 = 10), whose indices are 0 and 4
• 4 and 6 (4 + 6 = 10), whose indices are 2 and 3

Add all the indices together to get a return value of 9.

--hints--

pairwise([2, 3, 4, 6, 8], 10) should return 9.

assert.equal(pairwise([2, 3, 4, 6, 8], 10), 9);

pairwise([4, 1, 5, 2, 6, 3], 7) should return 15.

assert.equal(pairwise([4, 1, 5, 2, 6, 3], 7), 15);

pairwise([-30, -15, 5, 10, 15, -5, 20, -40], -20) should return 22.

assert.equal(pairwise([-30, -15, 5, 10, 15, -5, 20, -40], -20), 22);

pairwise([7, 9, 13, 19, 21, 6, 3, 1, 4, 8, 12, 22], 24) should return 10.

assert.equal(pairwise([7, 9, 13, 19, 21, 6, 3, 1, 4, 8, 12, 22], 24), 10);

--seed--

--seed-contents--

function pairwise(arr, target) {

  return arr;
}

--solutions--

function pairwise(arr, target) {
  let total = 0;

  for (let i = 0; i < arr.length; i++) {
    for (let j = i + 1; j < arr.length; j++) {
      if (arr[i] + arr[j] === target) {
        total += i + j;
      }
    }
  }

  return total;
}