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unordered_map::count

 

Finds the number of elements matching a specified key.

size_type count(const Key& keyval) const;

keyval

Key value to search for.

The member function returns the number of elements in the range delimited by unordered_map::equal_range(keyval).

Example

 

// std_tr1__unordered_map__unordered_map_count.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; 

    std::cout << "count('A') == " << c1.count('A') << std::endl; 
    std::cout << "count('b') == " << c1.count('b') << std::endl; 
    std::cout << "count('C') == " << c1.count('C') << std::endl; 

    return (0); 
    } 

 [c, 3] [b, 2] [a, 1]
count('A') == 0
count('b') == 1
count('C') == 0

Requirements

Header: <unordered_map>

Namespace: std

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