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unordered_map::equal_range

Finds range that matches a specified key.

std::pair<iterator, iterator>
    equal_range(const Key& keyval);
std::pair<const_iterator, const_iterator>
    equal_range(const Key& keyval) const;

keyval

Key value to search for.

The member function returns a pair of iterators X such that [X.first, X.second) delimits just those elements of the controlled sequence that have equivalent ordering with keyval. If no such elements exist, both iterators are end().

 

// std_tr1__unordered_map__unordered_map_equal_range.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; 
 
// display results of failed search 
    std::pair<Mymap::iterator, Mymap::iterator> pair1 = 
        c1.equal_range('x'); 
    std::cout << "equal_range('x'):"; 
    for (; pair1.first != pair1.second; ++pair1.first) 
        std::cout << " [" << pair1.first->first 
            << ", " << pair1.first->second << "]"; 
    std::cout << std::endl; 
 
// display results of successful search 
    pair1 = c1.equal_range('b'); 
    std::cout << "equal_range('b'):"; 
    for (; pair1.first != pair1.second; ++pair1.first) 
        std::cout << " [" << pair1.first->first 
            << ", " << pair1.first->second << "]"; 
    std::cout << std::endl; 
 
    return (0); 
    } 
 
 [c, 3] [b, 2] [a, 1]
equal_range('x'):
equal_range('b'): [b, 2]

Header: <unordered_map>

Namespace: std

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