When is your birthday? The math behind hash collisions
30 points
8 hours ago
| 3 comments
| 0xkrt26.github.io
| HN
pedrosbmartins
1 hour ago
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> What is the probability that you are sharing the same birthday with people around you?

> What if I told you that in a room with only 23 people there’s already a 50% chance for two of them to have matching birthdays?

I guess it's the subject shift from _you_ to _any two people from a group_ that creates the surprise in the birthday paradox. You definitely need way more than 23 randomly sampled people to get to a high probability that _you_ specifically share a birthday with one of them, and the result does not contradict that notion.

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pablowegw
3 hours ago
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And what are the odds of your birthday being exactly at the center of the (non-leap) year? That's my B'day. Cool!
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rossvc
3 hours ago
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50/50. Either it is or it isn’t!
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ChrisArchitect
2 hours ago
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Related today:

Ask HN: We just had an actual UUID v4 collision...

https://news.ycombinator.com/item?id=48060054

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