Namespaces
Variants

    std::erase, std::erase_if(std::vector)

    From cppreference.com
    See More

    [edit template]
     
    C++
     
    Containers library
     
    std::vector
    Member types
    Member functions
    Non-member functions
    (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
    Deduction guides(C++17)
     
    Defined in header <vector>
    (1)
    template< class T, class Alloc, class U > constexpr std::vector<T, Alloc>::size_type erase( std::vector<T, Alloc>& c, const U& value );
    		 (since C++20)
    (until C++26)
    template< class T, class Alloc, class U = T > constexpr std::vector<T, Alloc>::size_type erase( std::vector<T, Alloc>& c, const U& value );
    		 (since C++26)
    template< class T, class Alloc, class Pred > constexpr std::vector<T, Alloc>::size_type erase_if( std::vector<T, Alloc>& c, Pred pred );
    		 (2) (since C++20)
    1) Erases all elements that compare equal to value from the container. Equivalent to 
    auto it = std::remove(c.begin(), c.end(), value);
auto r = c.end() - it;
c.erase(it, c.end());
return r;
    2) Erases all elements that satisfy the predicate pred from the container. Equivalent to 
    auto it = std::remove_if(c.begin(), c.end(), pred);
auto r = c.end() - it;
c.erase(it, c.end());
return r;

    Parameters

    c - container from which to erase
    value - value to be removed
    pred - unary predicate which returns ​true if the element should be erased.

    The expression pred(v) must be convertible to bool for every argument v of type (possibly const) T, regardless of value category, and must not modify v. Thus, a parameter type of T&is not allowed, nor is T unless for T a move is equivalent to a copy(since C++11). ​

    Return value

    The number of erased elements.

    Complexity

    Linear.

    Notes

    Feature-test macro Value Std Feature
    __cpp_lib_algorithm_default_value_type 202403 (C++26) List-initialization for algorithm (1)

    Example

    Run this code
    #include <complex>
#include <iostream>
#include <numeric>
#include <string_view>
#include <vector>

void println(std::string_view comment, const auto& c)
{
    std::cout << comment << '[';
    bool first{true};
    for (const auto& x : c)
        std::cout << (first ? first = false, "" : ", ") << x;
    std::cout << "]\n";
}

int main()
{
    std::vector<char> cnt(10);
    std::iota(cnt.begin(), cnt.end(), '0');
    println("Initially, cnt = ", cnt);
    
    std::erase(cnt, '3');
    println("After erase '3', cnt = ", cnt);
    
    auto erased = std::erase_if(cnt, [](char x) { return (x - '0') % 2 == 0; });
    println("After erase all even numbers, cnt = ", cnt);
    std::cout << "Erased even numbers: " << erased << '\n';
    
    std::vector<std::complex<double>> nums{{2, 2}, {4, 2}, {4, 8}, {4, 2}};
    #ifdef __cpp_lib_algorithm_default_value_type
        std::erase(nums, {4, 2});
    #else
        std::erase(nums, std::complex<double>{4, 2});
    #endif
    println("After erase {4, 2}, nums = ", nums);
}

    Output: 

    Initially, cnt = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
After erase '3', cnt = [0, 1, 2, 4, 5, 6, 7, 8, 9]
After erase all even numbers, cnt = [1, 5, 7, 9]
Erased even numbers: 5
After erase {4, 2}, nums = [(2,2), (4,8)]

    See also

    		 removes elements satisfying specific criteria
    (function template) [edit]
    (C++20)(C++20)
    		 removes elements satisfying specific criteria
    (algorithm function object)[edit]