std::unordered_set::rehash(3)

💅 NAME 💅

std::unordered_set::rehash — bestie, it's the glow-up for your bucket count ✨

okay so real quick, the manual name is std::unordered_set::rehash and it lives in the C++ Standard Libary, and yes we are about to make your hash table move different 💖

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✨ Synopsis ✨

void rehash( size_type count );  (since C++11)

So what it does is it changes the number of buckets to some value n that is not less than count and satisfies

n >= size() / max_load_factor()

and then it rehashes the container — which is just a fancy way of saying it puts the elements into appropriate buckets considering that the total number of buckets has changed. like, everybody gets re-seated at the function, no cap 🎀

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🌸 Parameters 🌸

• count — the lower bound for the new number of buckets. it's a floor, not a demand, iykyk 🦋

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🫶 Return value 🫶

(none) — it gives you nothing back, it just does the thing. main character energy honestly 💅

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🔥 Complexity 🔥

• Average case: linear in the size of the container 🌈
• Worst case: quadratic 😭

so like, usually slay, but worst case it's giving slow. plan accordingly bestie 💀

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🍓 Notes 🍓

rehash(0) may be used to force an unconditional rehash — for real, zero is a valid move here 👑

like, say you temporarily increased max_load_factor() and that suspended automatic rehashing? this is your little "ok we're back, rehash everything now" button. iconic ✨

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🧚 See also 🧚

• reserve — reserves space for at least the specified number of elements and regenerates the hash table (public member function) 💜

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and that's the whole vibe check, bestie 🦋 this page was brought to you by http://cppreference.com (the source, ily) and it's dated 2024.06.10 🌸 go forth and rehash responsibly, mwah 💖