Program to print the series 2, 1, 4, 3, 6, 5, …. up to N terms

Given a number N, the task is to print the below pattern upto N terms:

2, 1, 4, 3, 6, 5, …. N terms

Examples:

Input: N = 4
Output: 2, 1, 4, 3

Explanation:
Nth Term = (N % 2 == 0) ? (N - 1) : (N + 1)
1st term = (1 % 2 == 0) ? (1 - 1) : (1 + 1)
         = (1 + 1)
         = 2
2nd term = (2 % 2 == 0) ? (2 - 1) : (2 + 1)
         = (2 - 1)
         = 1
3rd term = (3 % 2 == 0) ? (3 - 1) : (3 + 1)
         = (3 + 1)
         = 4
4th term = (4 % 2 == 0) ? (4 - 1) : (4 + 1)
         = (4 - 1)
         = 3
Therefore, Series = 2, 1, 4, 3

Input: N = 7
Output: 2, 1, 4, 3, 6, 5, 8

Formula:

Nth Term = (N % 2 == 0) ? (N - 1) : (N + 1)

Below is the solution to above problem:

C++

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// C++ program to print the series 
// 2, 1, 4, 3, 6, 5, …. up to N terms
#include <iostream>
using namespace std;
  
// Function to print the series
void printPattern(int N)
{
  
    for (int i = 1; i <= N; i++) {
  
        // Find and print the ith term
        cout <<" "<<((i % 2 == 0) ? (i - 1) : (i + 1));
    }
}
  
// Driver code
int main()
{
  
    // Get the value of N
    int N = 10;
  
    // Print the Series
    printPattern(N);
  
    return 0;
}

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Java

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// Java Program to print the series 
// 2, 1, 4, 3, 6, 5, …. up to N terms 
  
import java.util.*;
import java.lang.*;
import java.io.*;
  
class GFG
{
// Function to print the series 
static void printPattern(int N) 
    
    for (int i = 1; i <= N; i++) { 
    
        // Find and print the ith term 
        System.out.print(" "+((i % 2 == 0) ? (i - 1) : (i + 1))); 
    
    
// Driver code 
public static void main(String args[]) 
    
    // Get the value of N 
    int N = 10
    
    // Print the Series 
    printPattern(N); 
    
}

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Python3

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# Python program to print the series 
# 2, 1, 4, 3, 6, 5, …. up to N terms 
  
# Function to print the series 
def printPattern(N):
    for i in range(1, N + 1):
          
        # Find and print the ith term 
        print(i - 1 if i % 2 == 0 
                    else i + 1, end = " ")
  
# Driver code
N = 10
printPattern(N)
  
# This code is contributed by Shrikant13

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C#

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// C# program to print the series 
// 2, 1, 4, 3, 6, 5, …. up to N terms
using System;
  
class GFG
{
// Function to print the series
public void printPattern(int N)
{
  
    for (int i = 1; i <= N; i++)
    {
  
        // Find and print the ith term
        int a = ((i % 2 == 0) ? 
                      (i - 1) : (i + 1));
        Console.Write(" {0}", a);
    }
}
  
// Driver code
public static void Main()
{
    GFG g = new GFG();
      
    // Get the value of N
    int N = 10;
  
    // Print the Series
    g.printPattern(N);
}
}
  
// This code is contributed
// by Soumik

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PHP

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<?php
// PHP program to print the series 
// 2, 1, 4, 3, 6, 5, …. up to N terms
  
// Function to print the series
function printPattern($N)
{
  
    for ($i = 1; $i <= $N; $i++) 
    {
  
        // Find and print the ith term
        echo " " . (($i % 2 == 0) ? 
                    ($i - 1) : ($i + 1));
    }
}
  
// Driver code
  
// Get the value of N
$N = 10;
  
// Print the Series
printPattern($N);
  
// This code is contributed
// by ChitraNayal
?>

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Output:

2 1 4 3 6 5 8 7 10 9


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