代码

int binary_search(const unsigned *a, int n, unsigned x)
{
  int l = 0, r = n - 1;
  while(l < r) {
    int mid = (l + r) / 2;
    if(a[mid] > x) r = mid - 1;
    else if(a[mid] == x) return mid;
    else l = mid + 1;
  }
  return l;
}

评测结果