Reference
C Library
IOstream Library
Strings library
STL Containers
STL Algorithms
Miscellaneous
STL Containers
bitset
deque
list
map
multimap
multiset
priority_queue
queue
set
stack
vector
vector
comparison operators
vector::vector
vector::~vector
member functions:
vector::assign
vector::at
vector::back
vector::begin
vector::capacity
vector::clear
vector::empty
vector::end
vector::erase
vector::front
vector::get_allocator
vector::insert
vector::max_size
vector::operator=
vector::operator[]
vector::pop_back
vector::push_back
vector::rbegin
vector::rend
vector::reserve
vector::resize
vector::size
vector::swap


vector::resize

public member function
void resize ( size_type sz, T c = T() );

Change size

Resizes the vector to contain sz elements.

If sz is smaller than the current vector size, the content is reduced to its first sz elements, the rest being dropped.

If sz is greater than the current vector size, the content is expanded by inserting at the end as many copies of c as needed to reach a size of sz elements. This may cause a reallocation.

Notice that this function changes the actual content of the vector by inserting or erasing elements from the vector; It does not only change its storage capacity. To direct a change only in storage capacity, use vector::reserve instead.

Parameters

sz
New vector size, expressed in elements.
Member type size_type is an unsigned integral type.
c
Object whose content is copied to the added elements in case that sz is greater than the current vector size.
If not specified, the default constructor is used.
T is the first template parameter (the type of the elements stored in the vector).

Return Value

none

If a reallocation happens, it is performed using Allocator::allocate(), which may throw exceptions (for the default allocator, bad_alloc is thrown if the allocation request does not succeed).

Example

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
 
// resizing vector
#include <iostream>
#include <vector>
using namespace std;
int main ()
{
  vector<int> myvector;
  unsigned int i;
  // set some initial content:
  for (i=1;i<10;i++) myvector.push_back(i);
  myvector.resize(5);
  myvector.resize(8,100);
  myvector.resize(12);
  cout << "myvector contains:";
  for (i=0;i<myvector.size();i++)
    cout << " " << myvector[i];
  cout << endl;
  return 0;
}


The code sets a sequence of 9 numbers as an initial content for myvector. It then uses resize first to trim the vector to a size of 5, then to extend its size to 8 with values of 100 for its new elements, and finally it extends its size to 12 with their default values (for int elements this is zero). Output:
myvector contains: 1 2 3 4 5 100 100 100 0 0 0 0

Complexity

Linear on the number of elements inserted/erased (constructions/destructions).

See also

vector::size Return size (public member function)
vector::clear Clear content (public member function)
vector::max_size Return maximum size (public member function)