Array Element Swapping using c++

Source code:
#include<iostream>
#include<conio.h>
using namespace std;

int main()
{
    //variable declaration
    int arr[100],i,temp,size;

    cout<<"enter array size : ";
    cin>>size;
    cout<<"enter elements in to array : \n";
    for(i=0;i<size;++i)
    {
        cin>>arr[i];
    }
    cout<<"\narray before swaping elements : \n";
    for(i=0;i<size;++i)
    {
        cout<<arr[i]<<" ";
    }
    //element swapping logic
    for(i=1;i<size;i+=2)
    {
        temp=arr[i];
        arr[i]=arr[i-1];
        arr[i-1]=temp;
    }
    cout<<"\narray after swapping elements : \n";
    for(i=0;i<size;++i)
    {
         cout<<arr[i]<<" ";
    }

}

OUTPUT

 enter array size : 4
 enter elements in to array : 1 2 3 4
 array before swaping elements : 1 2 3 4
 array after swapping elements : 2 1 4 3