# std::list<T,Allocator>::resize

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< cpp‎ | container‎ | list

void resize( size_type count ); | (1) |
void resize( size_type count, const value_type& value ); | (2) |

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

If the current size is greater than count, the container is reduced to its first count elements.

If the current size is less than count,

1) additional default-inserted elements are appended
2) additional copies of value are appended.

### Parameters

count | - | new size of the container
value | - | the value to initialize the new elements with
Type requirements
- `T` must meet the requirements of DefaultInsertable in order to use overload (1).
- `T` must meet the requirements of CopyInsertable in order to use overload (2).

### Return value

(none)

### Complexity

Linear in the difference between the current size and count.

### 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`.

### Example

Run this code

    #include <list>
    #include <iostream>

    void print(auto rem, const std::list<int>& c)
    {
        for (std::cout << rem; const int el: c)
            std::cout << el << ' ';
        std::cout << '\n';
    }

    int main()
    {
        std::list<int> c = {1, 2, 3};
        print("The list 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);
    }

Output:

    The list holds: 1 2 3
    After resize up to 5: 1 2 3 0 0
    After resize down to 2: 1 2
    After resize up to 6 (initializer = 4): 1 2 4 4 4 4

### 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 132 | C++98 | random-access iterators were used to determine the erase range | use bidirectional iterators
LWG 679 | C++98 | `resize()` passed value by value | passes by const reference
LWG 1420 | C++98 | the behavior of resize(size()) was not specified | specified

### See also

size | returns the number of elements (public member function)
insert | inserts elements (public member function)
erase | erases elements (public member function)

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