binary search

BinarySearch.swift

func binarySearch(item: Int, in A: [Int]) -> Int? {
  
  var beg = 0
  var end = A.count - 1
  var result: Int?
  
  while end - beg >= 1 {
    
    var mid = (beg + end) / 2
    
    if item < A[mid] {
      end = mid - 1
      
    } else {
      beg = mid + 1
    }
    
    if A[mid] == item { result = mid; break }
    
    if end == beg && A[end] == item { result = mid; break }
    
  }
  return result
}