Problem

4/10

Pairwise permutation

Theory Click to read/hide

To change the value by index in the list, use name.set(index,value); 
  

arr.set(0,10);

Problem

Given a one-dimensional array of dimension N (2<=N<=20) N-even.
Swap pairs of its elements. That is, the first with the second, the third  with the fourth, etc.

Input: 
- the first line contains the number N - the number of array elements;
- the second line contains the values ​​of the array elements.

Output: you want to display the resulting array.
 
Examples
# Input Output
1 4
1 2 3 4 		2 1 4 3


time 1000 ms
memory 256 Mb
Rules for program design and list of errors in automatic problem checking

Teacher commentary

Insert the missing code snippets
Java
Write the program below 
import java.util.ArrayList;
import java.util.Scanner;
public class Main
{
    public static void main(String[] args) {
        int n;
        Scanner in = new Scanner(System.in);
        n = in.nextInt();

        ArrayList<Integer> arr = new ArrayList<Integer>();

        for(int i=0;i<n;i++) {
            int a = in.nextInt();
            arr.add(a);
        }
 
    for (Integer a: arr)
              {
                System.out.print(a+" ");
        }
    }
}

     

Program check result

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