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unordered_map::erase

Removes elements at specified positions.

iterator erase(iterator where);
iterator erase(iterator first, iterator last);
size_type erase(const Key& keyval);

Parameters

  • first
    Beginning of range to erase.

  • key
    Key value to erase.

  • last
    End of range to erase.

  • where
    Element to erase

Remarks

The first member function removes the element of the controlled sequence pointed to by where. The second member function removes the elements in the range [first, last). Both return an iterator that designates the first element remaining beyond any elements removed, or unordered_map::end() if no such element exists.

The third member removes the elements in the range delimited by unordered_map::equal_range(keyval). It returns the number of elements it removes.

The member functions never throw an exception.

Example

 

// std_tr1__unordered_map__unordered_map_erase.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; 
 
// erase an element and reinspect 
    Mymap::iterator it2 = c1.erase(c1.begin()); 
    std::cout << "*erase(begin()) == [" 
        << it2->first << ", " << it2->second << "]"; 
    std::cout << std::endl; 
 
// add elements and display " [e 5] [d 4] [b 2] [a 1]" 
    c1.insert(Mymap::value_type('d', 4)); 
    c1.insert(Mymap::value_type('e', 5)); 
 
    for (Mymap::const_iterator it = c1.begin(); 
        it != c1.end(); ++it) 
        std::cout << " [" << it->first << ", " << it->second << "]"; 
    std::cout << std::endl; 
 
// erase all but end; 
    it2 = c1.end(); 
    it2 = c1.erase(c1.begin(), --it2); 
    std::cout << "*erase(begin(), end()-1) == [" 
        << it2->first << ", " << it2->second << "]" << std::endl; 
    std::cout << "size() == " << c1.size() << std::endl; 
 
    return (0); 
    } 
 
 [c, 3] [b, 2] [a, 1]
*erase(begin()) == [b, 2]
 [e, 5] [d, 4] [b, 2] [a, 1]
*erase(begin(), end()-1) == [a, 1]
size() == 1

Requirements

Header: <unordered_map>

Namespace: std

See Also

Reference

<unordered_map>

unordered_map Class

unordered_map::clear