On: Show HN: Test if your (US) phone number is in the ...

[mckirk]

To be honest, I don't really know the rules governing US phone numbers and just did a cursory google search, which came up with the simple answer of "10 billion".

That is very likely quite an overestimation. But if I'm not mistaken, the limitations you describe only reduce the search space by 19% (since it's two 90%-steps).

[dotancohen → mckirk]

  100 * 0.1 = 10  // First  90% Reduction
  10  * 0.1 = 1   // Second 90% Reduction

[mckirk → dotancohen]

Not allowing a single digit to be 0 is a 10% reduction though, is it not?

[dotancohen → mckirk]

Oh, you're right! Thank you.

[mckirk → dotancohen]

No worries :)

I checked the math so many times because I was starting to suspect my mind was glitching, lol.