size() and resize() Functions in C++

This C++ program demonstrates size() and resize() functions on a vector. The function size() returns the size of the container and the function resize() resizes the container to the specified size and moves the elements to the new allocated space.

Here is the source code of the C++ program which demonstrates size() and resize() functions on a vector. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

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/*
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 * C++ Program to demonstrate size() and resize() functions on vector

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 */
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#include <iostream>
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#include <vector>
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#include <iomanip>
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using namespace std;
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```
 
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void print(vector <int> vs)
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{   
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    vector <int>::iterator i;
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    cout << "Vector elements : ";
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    for(i = vs.begin(); i != vs.end(); i++)

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    {
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        cout << setw(2) << *i << "  ";
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    }
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    cout << endl;
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}
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```
 
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int main()
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{
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    int arr[] = {10, 20, 30, 40, 50};
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    int alen  = sizeof(arr) / sizeof(int);

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    vector <int> vector(arr, arr + alen);

    cout << "Vector of size = " << vector.size() << endl;

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    print(vector);
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    vector.resize(2 * alen);
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    cout << "Vector resized to size = " << vector.size() << endl;

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    vector.assign(10, 10);
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    print(vector);
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}
```

$ a.out
Vector of size = 5
Vector elements : 10  20  30  40  50  
Vector resized to size = 10
Vector elements : 10  10  10  10  10  10  10  10  10  10