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unordered_set

unsorted set with operations O(1)

set basic opeartions are of O(log n); whereas unordered_set basic opeartions are of O(1),

caution

Unordered sets work with primitive types, but require a [custom hash function- use us_gu] for structures/classes like vectors and pairs.

info

Use case for unordered_set

  • check element present or not
caution

Only take basic primitive data types such as int, string, float, bool, long long, double

Cannot take other complex containers like:~

  • set<int>
  • < pair < int, int > >

Lookup Functions​

count()​

find()​

caution

Time Complexity:​

  • Average case: constant -- O(1)
  • Worst case: linear in container size -- -- O(n)

contains()​

dont'have lower_bound nd upper_bound​

unodered_set has no member lower_bound or upper_bound