# Reversal Algorithm for the Right Rotation of an Array in C++

Hello Folks, In this tutorial we are going to learn about the * reversal algorithm for the right rotation of an array in C++.* First, we will understand what do we mean by the

**. So, the right rotation of an array means rotation of an array in the**

*right rotation of an array***closed cycle**in the

**right direction**or the

**clockwise direction**.

Let us consider an example;

int arr[10] = {1 2 3 4 5 6 7 8 9 10}; So after right rotation by k amount(say 2); Roatated array will be; arr[10] = {9 10 1 2 3 4 5 6 7 8};

Although there are many algorithms to implement this yet we will only discuss the * reversal algorithm in this tutorial*.

## Reversal Algorithm for the Right Rotation of an Array and its Implementation in C++

**Algorithm**

- First, we will reverse the
**whole array**. - Then we will reverse the subarray from indices
**0 to k-1**, where**k is the rotating amount.** - Finally, we will reverse the subarray from indices
**k to n-1**, where**n is the size of the array.**

Example;

arr[10] = {1 2 3 4 5 6 7 8 9 10}; k = 6; // After First Step arr[10] = {10 9 8 7 6 5 4 3 2 1}; // After Second Step arr[10] = {5 6 7 8 9 10 4 3 2 1}; // After Last step // Roatated array arr[10] = {5 6 7 8 9 10 1 2 3 4};

In this way, we will get the rotated array. Now, let us see the **Implementation** of the following **Algorithm in C++.**

**Code**

**Code**

#include<bits/stdc++.h> using namespace std; int main() { // Given Array int arr[10] = {1,2,3,4,5,6,7,8,9,10}; // size of the array arr int n = sizeof(arr)/sizeof(arr[0]); // Printing the original array cout<<"Given Array - \n"; for(auto i: arr){ cout<<i<<" "; } cout<<"\n"; // Amount of the rotation as input int k; cin>>k; // Reverse whole array reverse(arr,arr+n); // Reverse subarray arr[0 to k-1] reverse(arr,arr+k); // Reverse subarray arr[k to n-1] reverse(arr+k,arr+n); // Rotated array cout<<"Array after rotation - \n"; for(auto i: arr){ cout<<i<<" "; } cout<<"\n"; return 0; }

**Inputs**

**Inputs**

1 2 6

**Outputs**

**Outputs**

Given Array - 1 2 3 4 5 6 7 8 9 10 Array after rotation - 10 1 2 3 4 5 6 7 8 9 Given Array - 1 2 3 4 5 6 7 8 9 10 Array after rotation - 9 10 1 2 3 4 5 6 7 8 Given Array - 1 2 3 4 5 6 7 8 9 10 Array after rotation - 5 6 7 8 9 10 1 2 3 4

**Time Complexity – O(n) Space Complexity – O(1)**

This is it for this tutorial.

Hope you like it.

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