Java Program for Reversal algorithm for array rotation Last Updated : 10 Oct, 2023 Summarize Comments Improve Suggest changes Share Like Article Like Report Write a function rotate(arr[], d, n) that rotates arr[] of size n by d elements. Example : Input : arr[] = [1, 2, 3, 4, 5, 6, 7] d = 2Output : arr[] = [3, 4, 5, 6, 7, 1, 2] Rotation of the above array by 2 will make array Algorithm : rotate(arr[], d, n) reverse(arr[], 1, d) ; reverse(arr[], d + 1, n); reverse(arr[], 1, n);Let AB are the two parts of the input array where A = arr[0..d-1] and B = arr[d..n-1]. The idea of the algorithm is : Reverse A to get ArB, where Ar is reverse of A.Reverse B to get ArBr, where Br is reverse of B.Reverse all to get (ArBr) r = BA.Example : Let the array be arr[] = [1, 2, 3, 4, 5, 6, 7], d =2 and n = 7A = [1, 2] and B = [3, 4, 5, 6, 7] Reverse A, we get ArB = [2, 1, 3, 4, 5, 6, 7]Reverse B, we get ArBr = [2, 1, 7, 6, 5, 4, 3]Reverse all, we get (ArBr)r = [3, 4, 5, 6, 7, 1, 2]Below is the implementation of the above approach: Java // Java program for reversal algorithm of array rotation import java.io.*; class LeftRotate { /* Function to left rotate arr[] of size n by d */ static void leftRotate(int arr[], int d) { if (d == 0) return; int n = arr.length; // in case the rotating factor is // greater than array length d = d % n; reverseArray(arr, 0, d - 1); reverseArray(arr, d, n - 1); reverseArray(arr, 0, n - 1); } /*Function to reverse arr[] from index start to end*/ static void reverseArray(int arr[], int start, int end) { int temp; while (start < end) { temp = arr[start]; arr[start] = arr[end]; arr[end] = temp; start++; end--; } } /*UTILITY FUNCTIONS*/ /* function to print an array */ static void printArray(int arr[]) { for (int i = 0; i < arr.length; i++) System.out.print(arr[i] + " "); } /* Driver program to test above functions */ public static void main(String[] args) { int arr[] = { 1, 2, 3, 4, 5, 6, 7 }; int n = arr.length; int d = 2; leftRotate(arr, d); // Rotate array by d printArray(arr); } } /*This code is contributed by Devesh Agrawal*/ Output3 4 5 6 7 1 2 Time Complexity: O(N)Auxiliary Space: O(1) Please refer complete article on Reversal algorithm for array rotation for more details! 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