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

Resizes the container to contain count elements, does nothing if count == size().

# Declarations

void resize( size_type count );

(constexpr since C++20)

void resize( size_type count, const value_type& value );

(constexpr since C++20)

# Parameters

• count: new size of the container
• value: the value to initialize the new elements with

# Notes

If value-initialization in overload (1) is undesirable, for example, if the elements are of non-class type and zeroing out is not needed, it can be avoided by providing a custom Allocator::construct. Vector capacity is never reduced when resizing to smaller size because that would invalidate all iterators, rather than only the ones that would be invalidated by the equivalent sequence of pop_back() calls.

# Example

#include <vector>
#include <iostream>
 
void print(auto rem, const std::vector<int>& c)
{
    for (std::cout << rem; const int el : c)
        std::cout << el << ' ';
    std::cout << '\n';
}
 
int main()
{
    std::vector<int> c = {1, 2, 3};
    print("The vector holds: ", c);
 
    c.resize(5);
    print("After resize up to 5: ", c);
 
    c.resize(2);
    print("After resize down to 2: ", c);
 
    c.resize(6, 4);
    print("After resize up to 6 (initializer = 4): ", c);
}

# Defect reports

# See also

• max_size
• size
• capacity
• empty