CODEWITHSUNDEEP
c++data-structuresvectorhashmap
orezvani
orezvani

Reputation: 3775

How to maintain a set of vectors with no repetitions

I have a program in c++ that is producing a lot of vectors of integers (each vector is sorted), and they are being produced very fast and in a large number, I need to keep track of them and remove the repetitions, and print them all in the end. What data structure should I use?

I tried using hash_map and unordered_map but I got lot's of errors and seems that they do not support hash map of vectors (so how they support strings though?) :

(.text+0xdc56): undefined reference to `std::tr1::hash<std::vector<int, std::allocator<int> > >::operator()(std::vector<int, std::allocator<int> >) const'
objects/Prog.o: In function `std::tr1::_Hashtable<std::vector<int, std::allocator<int> >, std::pair<std::vector<int, std::allocator<int> > const, int>, std::allocator<std::pair<std::vector<int, std::allocator<int> > const, int> >, std::_Select1st<std::pair<std::vector<int, std::allocator<int> > const, int> >, std::equal_to<std::vector<int, std::allocator<int> > >, std::tr1::hash<std::vector<int, std::allocator<int> > >, std::tr1::__detail::_Mod_range_hashing, std::tr1::__detail::_Default_ranged_hash, std::tr1::__detail::_Prime_rehash_policy, false, false, true>::_M_rehash(unsigned long)':
Prog.cpp:(.text._ZNSt3tr110_HashtableISt6vectorIiSaIiEESt4pairIKS3_iESaIS6_ESt10_Select1stIS6_ESt8equal_toIS3_ENS_4hashIS3_EENS_8__detail18_Mod_range_hashingENSE_20_Default_ranged_hashENSE_20_Prime_rehash_policyELb0ELb0ELb1EE9_M_rehashEm[std::tr1::_Hashtable<std::vector<int, std::allocator<int> >, std::pair<std::vector<int, std::allocator<int> > const, int>, std::allocator<std::pair<std::vector<int, std::allocator<int> > const, int> >, std::_Select1st<std::pair<std::vector<int, std::allocator<int> > const, int> >, std::equal_to<std::vector<int, std::allocator<int> > >, std::tr1::hash<std::vector<int, std::allocator<int> > >, std::tr1::__detail::_Mod_range_hashing, std::tr1::__detail::_Default_ranged_hash, std::tr1::__detail::_Prime_rehash_policy, false, false, true>::_M_rehash(unsigned long)]+0x126): undefined reference to `std::tr1::hash<std::vector<int, std::allocator<int> > >::operator()(std::vector<int, std::allocator<int> >) const'
collect2: ld returned 1 exit status
make: *** [run] Error 1

Is there any other way to get around this? Is there any other data structure with better efficiency?

Upvotes: 0

Views: 167

Answers (1)

David Mahone
David Mahone

Reputation: 237

You need to provide a hash function for vector to use unordered_map. The hash function for string is provided by default. Alternatively, you can use std::set. Elements of std::set are guaranteed to have no dupilcates.

Upvotes: 4

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