Left rotate an array by D places in C++

By Kunal Kamble

Hello, friends in this tutorial we will learn to left rotate an array by D places and write the code for it in C++.

An array is a collection of elements of similar data types stored in contiguous memory locations. It is used to store a collection of data. We can access the elements of an array by the index at which the element is stored.

Given an integer array of N elements, we have to rotate the array by D places.

For example, consider the following array of 9 elements from 1 to 9 and D=6

Hence after rotating the array by 6 places we get the following resultant array.

The approach is simple, consider Input array arr[] = [1, 2, 3, 4, 5, 6, 7, 8, 9], d = 6, n = 9

1. Store the first d elements in a temporary array temp[] = [1, 2, 3, 4, 5, 6]
2. Shift the remaining elements of the array toward the start of the array.
3. Store back the d elements to the array arr[] = [7, 8, 9, 1, 2, 3, 4, 5, 6]

C++ program to rotate the array by D places

Following is the code to left rotate the array by D places

#include<iostream>
using namespace std;

/* function which left rotate the array by D places */
void leftRotateByD(int *arr,int n,int d)
{
  /* storing 1st D elements in temporary array */
  int temp[d];
  for (int i=0;i<d;i++)
  {
    temp[i]=arr[i];
  }
  
  /* shifting remaining elements of the array */
  int x=0;
  for(int j=d;j<n;j++)
  {
    arr[x]=arr[j];
    x++;
  }
  
  /* storing back the D elements to the orignal array */
  x=0;
  for (int k=n-d;k<n;k++)
  {
    arr[k]=temp[x];
    x++;
  }
  
}
  

int main()
{
  int n,d;
  
  cout<<"Enter the size of array\n";
  cin>>n;
  
  int arr[n];
  cout<<"Enter the elements of array\n";
  for (int i=0;i<n;i++)
  {
    cin>>arr[i];
  }
  
  cout<<"Enter the value of D\n";
  cin>>d;
  
  /* function call to rotate the array */
  leftRotateByD(arr,n,d); 
    
  cout<<"Array after left rotation by D places\n";
  for (int i=0;i<n;i++)
  {
    cout<<arr[i]<<" ";
  }
  
  
  return 0;
}

OUTPUT:

Following is the output of the above program.

Enter the size of array
9

Enter the elements of array
1 2 3 4 5 6 7 8 9

Enter the value of D
6

Array after left rotation by D places
7 8 9 1 2 3 4 5 6

The time complexity of the program is O(N).