Hackerrank: Pairs Solution

1function binarySearch(A, x) {
2  const N = A.length
3  let begin = 0
4  let end = N - 1
5  let result = -1
6  while (begin <= end) {
7    let mid = Math.floor((begin + end) / 2)
8    if (A[mid] === x) {
9      result = mid
10      break
11    }
12    if (A[mid] > x) {
13      end = mid - 1
14    } else if (A[mid] < x) {
15      begin = mid + 1
16    }
17  }
18  return result
19}
20
21function pairs(k, arr) {
22  const sortedArr = Array.from(arr).sort((a, b) => a - b)
23  let count = 0
24  for (const a of arr) {
25    if (binarySearch(sortedArr, a + k) !== -1) {
26      count++
27    }
28  }
29  return count
30}