unordered_map::rehash

Article
03/04/2013

Régénère la table de hachage.

void rehash(size_type nbuckets);

Paramètres

nbuckets
Le nombre demandé de compartiments restant.

Notes

La fonction membre modifie le nombre de compartiments pour être au moins nbuckets et régénère la table de hachage si nécessaire.

Exemple

// std_tr1__unordered_map__unordered_map_rehash.cpp 
// compile with: /EHsc 
#include <unordered_map> 
#include <iostream> 
 
typedef std::unordered_map<char, int> Mymap; 
int main() 
    { 
    Mymap c1; 
 
    c1.insert(Mymap::value_type('a', 1)); 
    c1.insert(Mymap::value_type('b', 2)); 
    c1.insert(Mymap::value_type('c', 3)); 
 
// display contents " [c 3] [b 2] [a 1]" 
    for (Mymap::const_iterator it = c1.begin(); 
        it != c1.end(); ++it) 
        std::cout << " [" << it->first << ", " << it->second << "]"; 
    std::cout << std::endl; 
 
// inspect current parameters 
    std::cout << "bucket_count() == " << c1.bucket_count() << std::endl; 
    std::cout << "load_factor() == " << c1.load_factor() << std::endl; 
    std::cout << "max_load_factor() == " << c1.max_load_factor() << std::endl; 
    std::cout << std::endl; 
 
// change max_load_factor and redisplay 
    c1.max_load_factor(0.10f); 
    std::cout << "bucket_count() == " << c1.bucket_count() << std::endl; 
    std::cout << "load_factor() == " << c1.load_factor() << std::endl; 
    std::cout << "max_load_factor() == " << c1.max_load_factor() << std::endl; 
    std::cout << std::endl; 
 
// rehash and redisplay 
    c1.rehash(100); 
    std::cout << "bucket_count() == " << c1.bucket_count() << std::endl; 
    std::cout << "load_factor() == " << c1.load_factor() << std::endl; 
    std::cout << "max_load_factor() == " << c1.max_load_factor() << std::endl; 
 
    return (0); 
    }