std::vector<T,Allocator>::erase

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< cpp‎ | container‎ | vector

 
C++
 
Containers library
 
std::vector
Member types
Member functions
(C++23)
Element access
Iterators
(C++11)
(C++11)
(C++11)
(C++11)
Capacity
(DR*)
Modifiers
(C++11)
(C++23)
vector::erase
(C++11)
(C++23)
Non-member functions
(C++20)(C++20)
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
Deduction guides(C++17)
 
(1)
iterator erase( iterator pos );
 (until C++11)
iterator erase( const_iterator pos );
 (since C++11)
(until C++20)
constexpr iterator erase( const_iterator pos );
 (since C++20)
(2)
iterator erase( iterator first, iterator last );
 (until C++11)
iterator erase( const_iterator first, const_iterator last );
 (since C++11)
(until C++20)
constexpr iterator erase( const_iterator first, const_iterator last );
 (since C++20)

Erases the specified elements from the container.

1) Removes the element at pos.
2) Removes the elements in the range [first, last).

Iterators (including the end() iterator) and references to the elements at or after the point of the erase are invalidated.

The iterator pos must be valid and dereferenceable. Thus the end() iterator (which is valid, but is not dereferenceable) cannot be used as a value for pos.

The iterator first does not need to be dereferenceable if first == last: erasing an empty range is a no-op.

Parameters

pos - iterator to the element to remove
first, last - range of elements to remove
Type requirements
-
T must meet the requirements of MoveAssignable.

Return value

Iterator following the last removed element.

1) If pos refers to the last element, then the end() iterator is returned.
2) If last == end() prior to removal, then the updated end() iterator is returned.
If [first, last) is an empty range, then last is returned.

Exceptions

Does not throw unless an exception is thrown by the assignment operator of T.

Complexity

Linear: the number of calls to the destructor of T is the same as the number of elements erased, the assignment operator of T is called the number of times equal to the number of elements in the vector after the erased elements

Notes

When container elements need to be erased based on a predicate, rather than iterating the container and calling unary erase, the iterator range overload is generally used with std::remove()/std::remove_if() to minimise the number of moves of the remaining (non-removed) elements, this is the erase-remove idiom. std::erase_if() replaces the erase-remove idiom. (since C++20)

Example

Run this code
#include <vector>
#include <iostream>
 
 
void print_container(const std::vector<int>& c) 
{
    for (int i : c)
        std::cout << i << " ";
    std::cout << '\n';
}
 
int main( )
{
    std::vector<int> c{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    print_container(c);
 
    c.erase(c.begin());
    print_container(c);
 
    c.erase(c.begin() + 2, c.begin() + 5);
    print_container(c);
 
    // Erase all even numbers
    for (std::vector<int>::iterator it = c.begin(); it != c.end();)
    {
        if (*it % 2 == 0)
            it = c.erase(it);
        else
            ++it;
    }
    print_container(c);
}

Output: 

0 1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 6 7 8 9
1 7 9

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 151 C++98 first was required to be dereferenceable, which
made the behavior of clearing an empty vector undefined 		not required if
first == last
LWG 414 C++98 iterators at the point of erase were not invalidated they are also invalidated

See also

(C++20)
 erases all elements satisfying specific criteria
(function template)
clears the contents
(public member function)
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