Rotate Array

Problem Statement - link #

Given an unsorted array arr[] of size N. Rotate the array to the left (counter-clockwise direction) by D steps, where D is a positive integer.

Your Task: Complete the function rotateArr() which takes the array, D and N as input parameters and rotates the array by D elements. The array must be modified in-place without using extra space.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(1).

Examples #

Example 1:

Input:
N = 5, D = 2
arr[] = {1,2,3,4,5}
Output: 3 4 5 1 2
Explanation: 1 2 3 4 5  when rotated
by 2 elements, it becomes 3 4 5 1 2.

Example 2:

Input:
N = 10, D = 3
arr[] = {2,4,6,8,10,12,14,16,18,20}
Output: 8 10 12 14 16 18 20 2 4 6
Explanation: 2 4 6 8 10 12 14 16 18 20 
when rotated by 3 elements, it becomes 
8 10 12 14 16 18 20 2 4 6.

Constraints #

• 1 <= N,D <= 10^6
• 0 <= A[i] <= 10^5

Solutions #

class Solution{
public:
    //Function to rotate an array by d elements in counter-clockwise direction. 
    void rotateArr(int a[], int d, int n){
        // code here
        d = d%n;
        int temp[d];
        for(int i=0;i<d;i++)
            temp[i] = a[i];
        for(int i=d;i<n;i++)
            a[i-d] = a[i];
        for(int i=0;i<d;i++)
            a[n-d+i] = temp[i];
    }
};