Java Program For Array Rotation

03 Mar, 2021
Write a function rotate(ar[], d, n) that rotates arr[] of size n by d elements.
Rotation of the above array by 2 will make array
METHOD 1 (Using temp array)
Input arr[] = [1, 2, 3, 4, 5, 6, 7], d = 2, n =7
1) Store d elements in a temp array
   temp[] = [1, 2]
2) Shift rest of the arr[]
   arr[] = [3, 4, 5, 6, 7, 6, 7]
3) Store back the d elements
   arr[] = [3, 4, 5, 6, 7, 1, 2]
Time complexity : O(n)Auxiliary Space : O(d)
METHOD 2 (Rotate one by one)
leftRotate(arr[], d, n)
start
  For i = 0 to i < d
    Left rotate all elements of arr[] by one
end
To rotate by one, store arr[0] in a temporary variable temp, move arr[1] to arr[0], arr[2] to arr[1] ...and finally temp to arr[n-1]
Let us take the same example arr[] = [1, 2, 3, 4, 5, 6, 7], d = 2Rotate arr[] by one 2 timesWe get [2, 3, 4, 5, 6, 7, 1] after first rotation and [ 3, 4, 5, 6, 7, 1, 2] after second rotation.
class RotateArray {    /*Function to left rotate arr[] of size n by d*/    void leftRotate(int arr[], int d, int n)     {        int i;        for (i = 0; i < d; i++)            leftRotatebyOne(arr, n);    }      void leftRotatebyOne(int arr[], int n)     {        int i, temp;        temp = arr[0];        for (i = 0; i < n - 1; i++)            arr[i] = arr[i + 1];        arr[i] = temp;    }      /* utility function to print an array */    void printArray(int arr[], int size)     {        int i;        for (i = 0; i < size; i++)            System.out.print(arr[i] + " ");    }      // Driver program to test above functions    public static void main(String[] args)     {        RotateArray rotate = new RotateArray();        int arr[] = {1, 2, 3, 4, 5, 6, 7};        rotate.leftRotate(arr, 2, 7);        rotate.printArray(arr, 7);    }}  // This code has been contributed by Mayank Jaiswal
Output :
3 4 5 6 7 1 2 

Time complexity : O(n * d)Auxiliary Space : O(1)METHOD 3 (A Juggling Algorithm)This is an extension of method 2. Instead of moving one by one, divide the array in different setswhere number of sets is equal to GCD of n and d and move the elements within sets.If GCD is 1 as is for the above example array (n = 7 and d =2), then elements will be moved within one set only, we just start with temp = arr[0] and keep moving arr[I+d] to arr[I] and finally store temp at the right place.
Here is an example for n =12 and d = 3. GCD is 3 and
Let arr[] be {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}

a)    Elements are first moved in first set – (See below diagram for this movement)



          arr[] after this step --> {4 2 3 7 5 6 10 8 9 1 11 12}

b)    Then in second set.
          arr[] after this step --> {4 5 3 7 8 6 10 11 9 1 2 12}

c)    Finally in third set.
          arr[] after this step --> {4 5 6 7 8 9 10 11 12 1 2 3}

class RotateArray {    /*Function to left rotate arr[] of size n by d*/    void leftRotate(int arr[], int d, int n)     {        int i, j, k, temp;        for (i = 0; i < gcd(d, n); i++)         {            /* move i-th values of blocks */            temp = arr[i];            j = i;            while (true)             {                k = j + d;                if (k >= n)                     k = k - n;                if (k == i)                     break;                arr[j] = arr[k];                j = k;            }            arr[j] = temp;        }    }      /*UTILITY FUNCTIONS*/          /* function to print an array */    void printArray(int arr[], int size)     {        int i;        for (i = 0; i < size; i++)            System.out.print(arr[i] + " ");    }      /*Function to get gcd of a and b*/    int gcd(int a, int b)     {        if (b == 0)            return a;        else            return gcd(b, a % b);    }      // Driver program to test above functions    public static void main(String[] args) {        RotateArray rotate = new RotateArray();        int arr[] = {1, 2, 3, 4, 5, 6, 7};        rotate.leftRotate(arr, 2, 7);        rotate.printArray(arr, 7);    }}  // This code has been contributed by Mayank Jaiswal
Output :
3 4 5 6 7 1 2 

Time complexity : O(n)Auxiliary Space : O(1)
Please refer complete article on Program for array rotation for more details!
ManasChhabra2
Akanksha_Rai
Java Programs
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.