C++ STL vector, capacity() and size() code example

 

Compiler: Visual C++ Express Edition 2005

Compiled on Platform: Windows XP Pro SP2

Header file: Standard

Additional library: none/default

Additional project setting: Set project to be compiled as C++

Project -> your_project_name Properties -> Configuration Properties -> C/C++ -> Advanced -> Compiled As: Compiled as C++ Code (/TP)

Other info: none

To do: Using the C++ capacity() to return the number of elements that the vector could contain without allocating more storage and size() to return the number of elements in the vector in C++ programming

To show: How to use the C++ capacity() to return the number of elements that the vector could contain without allocating more storage and size() to return the number of elements in the vector in C++ programming

 

// C++ STL vector, capacity() and size()

#include <vector>

#include <iostream>

using namespace std;

 

int main(void)

{

// vector container

vector <int> vec1;

unsigned int i;

 

// push data into container

vec1.push_back(3);

vec1.push_back(1);

vec1.push_back(6);

 

// print the data

cout<<"vec1 vector data: ";

for(i=0; i<vec1.size(); ++i)

cout<<vec1[i]<<' ';

cout<<endl;

cout<<"Operation: vec1.capacity();"<<endl;

cout<<"The length of storage allocated is "<<vec1.capacity()<<endl;

 

// push more data and print

vec1.push_back(10);

vec1.push_back(12);

vec1.push_back(4);

cout<<"\nnew vec1 vector data after push_back(): ";

for(i=0; i<vec1.size(); ++i)

cout<<vec1[i]<<' ';

cout<<endl;

cout<<"The length of storage allocated is now "<<vec1.capacity()<<endl;

return 0;

}

 

Output examples:

 

vec1 vector data: 3 1 6

Operation: vec1.capacity();

The length of storage allocated is 3

new vec1 vector data after push_back(): 3 1 6 10 12 4

The length of storage allocated is now 6

Press any key to continue . . .

 

 

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