vector - C++ - Optimal way to use multiple values as a key in unordered_map -

i'm programming class working state-spaces. problem is, don't know, what's ideal way use multiple values key in unordered_map.

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it's supposed work way:

i create state object values <1;0;8>, it'll inserted hashmap <1;0;8>:pointer_to_object. want hashmap because need find objects fast possible.

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i thought using vector or tuple.

is possible use 1 of them key unordered_map without specifying size in advance?

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edit:

i've tried use code recommended @the_mandrill this:

template <class t> typedef std::unordered_map<std::vector<t>, state<t>*, boost::hash<std::vector<t>> map;  template <class t> size_t hash_value(const std::vector<t>& vec) {     std::size_t seed = 0;     (const auto& val : vec) {       boost::hash_combine(seed, val);     }     return seed; } 

but i'm getting error:

statespacelib.cpp:79:83: error: template argument 3 invalid  typedef std::unordered_map<std::vector<t>, state<t>*, boost::hash<std::vector<t>> map;                                                                                    ^ statespacelib.cpp:79:1: error: template declaration of ‘typedef’  typedef std::unordered_map<std::vector<t>, state<t>*, boost::hash<std::vector<t>> map;  ^ 

you should able use vector - either on own or wrap in struct other state data need, , if have access boost use hash_combine:

typedef std::unordered_map<std::vector<int>, objectpointer, boost::hash<std::vector<int>> map;  size_t hash_value(const std::vector<int>& vec) {     std::size_t seed = 0;     (const auto& val : vec) {       boost::hash_combine(seed, val);     }     return seed;  }