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Print array after it is right rotated K times

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  • Difficulty Level : Easy
  • Last Updated : 11 Jun, 2022

Given an Array of size N and a values K, around which we need to right rotate the array. How to quickly print the right rotated array?
Examples : 
 

Input: Array[] = {1, 3, 5, 7, 9}, K = 2.
Output: 7 9 1 3 5
Explanation:
After 1st rotation - {9, 1, 3, 5, 7}
After 2nd rotation - {7, 9, 1, 3, 5}

Input: Array[] = {1, 2, 3, 4, 5}, K = 4.
Output: 2 3 4 5 1      

 

Approach:
 

  1. We will first take mod of K by N (K = K % N) because after every N rotation array will become the same as the initial array. 
     
  2. Now, we will iterate the array from i = 0 to i = N-1 and check, 
    • If i < K, Print rightmost Kth element (a[N + i -K]). Otherwise, 
       
    • Print array after ‘K’ elements (a[i – K]). 
       

Below is the implementation of the above approach. 
 

C++




// C++ implementation of right rotation
// of an array K number of times
#include<bits/stdc++.h>
using namespace std;
 
// Function to rightRotate array
void RightRotate(int a[], int n, int k)
{
     
    // If rotation is greater
    // than size of array
    k = k % n;
 
    for(int i = 0; i < n; i++)
    {
       if(i < k)
       {
            
           // Printing rightmost
           // kth elements
           cout << a[n + i - k] << " ";
       }
       else
       {
            
           // Prints array after
           // 'k' elements
           cout << (a[i - k]) << " ";
       }
    }
    cout << "\n";
}
     
// Driver code
int main()
{
    int Array[] = { 1, 2, 3, 4, 5 };
    int N = sizeof(Array) / sizeof(Array[0]);
    int K = 2;
     
    RightRotate(Array, N, K);
}
 
// This code is contributed by Surendra_Gangwar


Java




// Java Implementation of Right Rotation
// of an Array K number of times
import java.util.*;
import java.lang.*;
import java.io.*;
 
class Array_Rotation
{
 
// Function to rightRotate array
static void RightRotate(int a[],
                        int n, int k)
{
     
    // If rotation is greater
    // than size of array
    k=k%n;
 
    for(int i = 0; i < n; i++)
    {
        if(i<k)
        {
            // Printing rightmost
            // kth elements
            System.out.print(a[n + i - k]
                             + " ");
        }
        else
        {
            // Prints array after
            // 'k' elements
            System.out.print(a[i - k]
                             + " ");
        }
    }
    System.out.println();
}
     
// Driver program
public static void main(String args[])
{
    int Array[] = {1, 2, 3, 4, 5};
    int N = Array.length;
 
    int K = 2;
    RightRotate(Array, N, K);
 
}
}
// This code is contributed by M Vamshi Krishna


Python3




# Python3 implementation of right rotation
# of an array K number of times
 
# Function to rightRotate array
def RightRotate(a, n, k):
 
    # If rotation is greater
    # than size of array
    k = k % n;
 
    for i in range(0, n):
 
        if(i < k):
 
            # Printing rightmost
            # kth elements
            print(a[n + i - k], end = " ");
 
        else:
 
            # Prints array after
            # 'k' elements
            print(a[i - k], end = " ");
 
    print("\n");
 
# Driver code
Array = [ 1, 2, 3, 4, 5 ];
N = len(Array);
K = 2;
     
RightRotate(Array, N, K);
 
# This code is contributed by Code_Mech


C#




// C# implementation of right rotation
// of an array K number of times
using System;
class GFG{
 
// Function to rightRotate array
static void RightRotate(int []a,
                        int n, int k)
{
 
    // If rotation is greater
    // than size of array
    k = k % n;
 
    for(int i = 0; i < n; i++)
    {
       if(i < k)
       {
            
           // Printing rightmost
           // kth elements
           Console.Write(a[n + i - k] + " ");
       }
       else
       {
            
           // Prints array after
           // 'k' elements
           Console.Write(a[i - k] + " ");
       }
    }
    Console.WriteLine();
}
     
// Driver code
public static void Main(String []args)
{
    int []Array = { 1, 2, 3, 4, 5 };
    int N = Array.Length;
    int K = 2;
     
    RightRotate(Array, N, K);
}
}
 
// This code is contributed by Rohit_ranjan


Javascript




// Javascript implementation of right rotation
// of an array K number of times
 
// Function to rightRotate array
function RightRotate(a, n, k)
{
 
    // If rotation is greater
    // than size of array
    k = k % n;
 
    for (let i = 0; i < n; i++) {
        if (i < k) {
 
            // Printing rightmost
            // kth elements
            document.write(a[n + i - k] + " ");
        }
        else {
 
            // Prints array after
            // 'k' elements
            document.write((a[i - k]) + " ");
        }
    }
    document.write("<br>");
}
 
// Driver code
let Array = [1, 2, 3, 4, 5];
let N = Array.length;
let K = 2;
 
RightRotate(Array, N, K);
 
// This code is contributed by gfgking.


Output

4 5 1 2 3 

Time complexity : O(n) 
Auxiliary Space : O(1)
 

Method 2: Reversing the array 

Approach: The approach is simple yet optimized. The idea is to reverse the array three times. For the first time we reverse only the last k elements. Second time we will reverse first n-k(n=size of array) elements. Finally we will get our rotated array by reversing the entire array.

Code:

C++




// C++ program to rotate right an array  by K times
#include <iostream>
using namespace std;
int main()
{
    int arr[] = { 1, 3, 5, 7, 9, 11 };
    int n = sizeof(arr) / sizeof(arr[0]);
    int k = 3; //No. of rotations
    k = k % n;
    int i, j;
    // Reverse last k numbers
    for (i = n - k, j = n - 1; i < j; i++, j--) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
    // Reverse the first n-k terms
    for (i = 0, j = n - k - 1; i < j; i++, j--) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
    // Reverse the entire array
    for (i = 0, j = n - 1; i < j; i++, j--) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
 
    // Print the rotated array
    for (int i = 0; i < n; i++) {
        cout << arr[i] << " ";
    }
 
    return 0;
}


C




// C program to rotate right an array  by K times
#include <stdio.h>
// using namespace std;
int main()
{
    int arr[] = { 1, 3, 5, 7, 9, 11 };
    int n = sizeof(arr) / sizeof(arr[0]);
    int k = 3; //No. of rotations
    k = k % n;
    int i, j;
    // Reverse last k numbers
    for (i = n - k, j = n - 1; i < j; i++, j--) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
    // Reverse the first n-k terms
    for (i = 0, j = n - k - 1; i < j; i++, j--) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
    // Reverse the entire array
    for (i = 0, j = n - 1; i < j; i++, j--) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
 
    // Print the rotated array
    for (int i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
 
    return 0;
}


Java




// JAVA program to rotate right an array  by K times
import java.io.*;
class GFG {
    public static void main(String[] args)
    {
        int arr[] = new int[] { 1, 3, 5, 7, 9, 11 };
        int n = arr.length;
        int k = 3; // No. of rotations
        k = k % n;
        int i, j;
        // Reverse last k numbers
        for (i = n - k, j = n - 1; i < j; i++, j--) {
            int temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
        }
        // Reverse the first n-k terms
        for (i = 0, j = n - k - 1; i < j; i++, j--) {
            int temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
        }
        // Reverse the entire array
        for (i = 0, j = n - 1; i < j; i++, j--) {
            int temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
        }
 
        // Print the rotated array
        for (int t = 0; t < n; t++) {
            System.out.print(arr[t] + " ");
        }
    }
}
 
// This code is contributed by Taranpreet


Output

7 9 11 1 3 5 

Complexity Analysis:

Time Complexity: O(N).

Auxiliary Space: O(1).

Please see following posts for other methods of array rotation: 

https://www.geeksforgeeks.org/print-array-after-it-is-right-rotated-k-times-set-2/


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