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Circular rotation of an array using deque in C++

  • Difficulty Level : Easy
  • Last Updated : 23 Sep, 2019

Given an array arr[] of integers and another integer D, the task is to perform D circular rotations on the array and print the modified array.

Examples:

Input: Arr[] = {1, 2, 3, 4, 5, 6}, D = 2
Output: 5 6 1 2 3 4

Input: Arr[] = {1, 2, 3}, D = 2
Output: 2 3 1

Approach:
Using Deque in C++, a rotation can be performed deleting the last element from the deque and inserting it at the beginning of the same deque.



Similarly, all the required rotations can be performed and then print the contents of the modified deque to get the required rotated array.

If the number of rotations is more than the size of the deque then just take the mod with N, So, D = D%N.
Where D is the number of rotations and N is the size of the deque.

Below is the implementation of the above approach:




// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
  
// Function to circular rotate
// the array by d elements
void rotate(deque<int> deq,
            int d, int n)
{
    // Push first d elements
    // from last to the beginning
    for (int i = 0; i < d; i++) {
        int val = deq.back();
        deq.pop_back();
        deq.push_front(val);
    }
  
    // Print the rotated array
    for (int i = 0; i < n; i++) {
        cout << deq[i] << " ";
    }
    cout << endl;
}
  
// Driver code
int main()
{
    deque<int> v = { 1, 2, 3, 4, 5, 6, 7 };
    int n = v.size();
    int d = 5;
  
    rotate(v, d % n, n);
}
Output:
3 4 5 6 7 1 2

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