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In the USA. They range from 4 (St. Helena) to 13 (Austria), I believe.
by WaitWaitWha 4y ago
In the USA.
They range from 4 (St. Helena) to 13 (Austria), I believe.
- RL_Quine 4y agoIt's typically smaller though, not every phone number is allocated and many are in sequential groups. Some are special cased, you don't need to search any number matching `****555***` in north america for example, which cuts down on the search space quite a bit.
- mrb 4y ago"Quite a bit"? Filtering out ***555**** removes only 0.1% of phone numbers ;)
- RL_Quine 4y agoThat's one example of an invalid range, not all of them. Lots of the area codes in north america just haven't been used for one reason or another.
- tomjakubowski 4y agoI didn't do the math here but: Filtering out 5*... would remove 10% of the search space. (dots mean "followed by more stars") Filtering out *5*... would remove 1%. So wouldn't ***555**** remove closer to 0.01%, not 0.1%?
- 8organicbits 4y agoTry the math, this is a good problem to work through. The position of the 5 doesn't impact the search space like that. 10% of the 10 digit numbers start with a 5. 10% of the 10 digit numbers end with a 5. 5... in your example shouldn't be 1%.
- coder543 4y agoSt Helena changed to 5 digits nearly 7 years ago.
- InfoSecErik 4y agohttps://en.wikipedia.org/wiki/List_of_mobile_telephone_prefixes_by_country https://en.wikipedia.org/wiki/List_of_mobile_telephone_prefi...