Question

I want to store strings and issue each with a unique ID number (an index would be fine). I would only need one copy of each string and I require quick lookup. I check if the string exist in the table often enough that i notice a performance hit. Whats the best container to use for this and how do i lookup if the string exist?

Answer 1

I would suggest tr1::unordered_map. It is implemented as a hashmap so it has an expected complexity of O(1) for lookups and a worst case of O(n). There is also a boost implementation if your compiler doesn’t support tr1.

#include <string> #include <iostream> #include <tr1/unordered_map>  using namespace std;  int main() {     tr1::unordered_map<string, int> table;      table['One'] = 1;     table['Two'] = 2;      cout << 'find(\'One\') == ' << boolalpha << (table.find('One') != table.end()) << endl;      cout << 'find(\'Three\') == ' << boolalpha << (table.find('Three') != table.end()) << endl;       return 0; }