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C++ Program for Program to cyclically rotate an array by one

  • Last Updated : 26 Dec, 2021

Given an array, cyclically rotate the array clockwise by one. 

Examples:  

Input:  arr[] = {1, 2, 3, 4, 5}
Output: arr[] = {5, 1, 2, 3, 4}

Following are steps. 
1) Store last element in a variable say x. 
2) Shift all elements one position ahead. 
3) Replace first element of array with x.
 

C++




// C++ code for program 
// to cyclically rotate
// an array by one
# include <iostream>
using namespace std;
  
void rotate(int arr[], int n)
{
    int x = arr[n - 1], i;
    for (i = n - 1; i > 0; i--)
    arr[i] = arr[i - 1]; 
    arr[0] = x;
}
  
// Driver code
int main() 
{
    int arr[] = {1, 2, 3, 4, 5}, i;
    int n = sizeof(arr) / 
            sizeof(arr[0]);
  
    cout << "Given array is 
";
    for (i = 0; i < n; i++)
        cout << arr[i] << ' ';
  
    rotate(arr, n);
  
    cout << "
Rotated array is
";
    for (i = 0; i < n; i++)
        cout << arr[i] << ' ';
  
    return 0;
}
  
// This code is contributed by jit_t
Output
Given array is 
1 2 3 4 5 

Rotated array is
5 1 2 3 4 

Time Complexity: O(n) As we need to iterate through all the elements 
Auxiliary Space: O(1)
The above question can also be solved by using reversal algorithm.

Another approach:

We can use two pointers, say i and j which point to first and last element of array respectively. As we know in cyclic rotation we will bring last element to first and shift rest in forward direction, so start swaping arr[i] and arr[j] and keep j fixed and i moving towards j.  Repeat till i is not equal to j.

C++




#include <iostream>
using namespace std;
  
void rotate(int arr[], int n)
{
    int i = 0, j = n-1; // i and j pointing to first and last element respectively
    while(i != j){
    swap(arr[i], arr[j]);
    i++;
    }
}
  
// Driver code
int main() 
{
    int arr[] = {1, 2, 3, 4, 5}, i;
    int n = sizeof(arr) / 
            sizeof(arr[0]);
  
    cout << "Given array is \n";
    for (i = 0; i < n; i++)
        cout << arr[i] << " ";
  
    rotate(arr, n);
  
    cout << "\nRotated array is\n";
    for (i = 0; i < n; i++)
        cout << arr[i] << " ";
  
    return 0;
}
Output
Given array is 
1 2 3 4 5 
Rotated array is
5 1 2 3 4 


Please refer complete article on Program to cyclically rotate an array by one for more details!


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