unorder set in c++
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unordered_set<data_type> set_name;
set_name.insert(1);
set_name.insert(4);
set_name.insert(9);
set_name.insert(2);
set_name.insert(1);
set_name.insert(10);
unordered_set: 10, 2, 1, 9, 4
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The structure unordered_set uses hashing, and its operations work in O(1) time
on average.