二分查找

binarySearch.cpp

template <typename Comparable>
int binarySearch(const vector<Comparable>& a, const Comparable& x) {
  int low = 0, high = a.size() - 1;

  while (low <= high) {
    int mid = (low + high) / 2;

    if (a[mid] < x) 
      low = mid + 1;
    else(a[mid] > x)
      high = mid - 1;
    else 
      return mid;
  }

  return NOT_FOUND;
}