All the code about how to find black hole numbers using Python.
The basic way to find black numbers, slow.
Randomly pick 100000 numbers to estimate time needed in Version1.0.
Try to avoid repeated calculation. But because
elif num in calculated
need to compare every number in calculated with "num", actually much slower then Version1.0.
Using binary search to check whether "num" is in "calculated". But need to sort "calculated" every time add number in, even slower than Version2.0.
Using binary search both to check whether in "calculated" but also where to add "num" so that the list will alway be sorted and can use binary search. Save 72% of the time based on time needed for six-digit black hole number using Version1.0.
Using dict as ordered set, same principle but different realization, save 90% of the time based on time needed for six-digit black hole number using Version1.0.
Use the method Riddle to avoid "equal" numbers in the situation of finding black hole numbers. Save 1% more than Version2.3.
Using a generator to directly generate "candidates" for search. And effectively lower the time needed for searching.