Reversal algorithm for right rotation of an array
Given an array, right rotate it by k elements.
After K=3 rotation
Examples:
Input: arr[] = {1, 2, 3, 4, 5,
6, 7, 8, 9, 10}
k = 3
Output: 8 9 10 1 2 3 4 5 6 7
Input: arr[] = {121, 232, 33, 43 ,5}
k = 2
Output: 43 5 121 232 33
Note : In the below solution, k is assumed to be smaller than or equal to n. We can easily modify the solutions to handle larger k values by doing k = k % n
Algorithm:
rotate(arr[], d, n) reverseArray(arr[], 0, n-1) ; reverse(arr[], 0, d-1); reverse(arr[], d, n-1);
Below is the implementation of above approach:
C++
// C++ program for right rotation of // an array (Reversal Algorithm) #include <bits/stdc++.h> /*Function to reverse arr[] from index start to end*/void reverseArray(int arr[], int start, int end) { while (start < end) { std::swap(arr[start], arr[end]); start++; end--; } } /* Function to right rotate arr[] of size n by d */void rightRotate(int arr[], int d, int n) { reverseArray(arr, 0, n-1); reverseArray(arr, 0, d-1); reverseArray(arr, d, n-1); } /* function to print an array */void printArray(int arr[], int size) { for (int i = 0; i < size; i++) std::cout << arr[i] << " "; } // driver code int main() { int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; int n = sizeof(arr)/sizeof(arr[0]); int k = 3; rightRotate(arr, k, n); printArray(arr, n); return 0; } |
Java
// Java program for right rotation of // an array (Reversal Algorithm) import java.io.*; class GFG { // Function to reverse arr[] // from index start to end static void reverseArray(int arr[], int start, int end) { while (start < end) { int temp = arr[start]; arr[start] = arr[end]; arr[end] = temp; start++; end--; } } // Function to right rotate // arr[] of size n by d static void rightRotate(int arr[], int d, int n) { reverseArray(arr, 0, n - 1); reverseArray(arr, 0, d - 1); reverseArray(arr, d, n - 1); } // Function to print an array static void printArray(int arr[], int size) { for (int i = 0; i < size; i++) System.out.print(arr[i] + " "); } public static void main (String[] args) { int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; int n = arr.length; int k = 3; rightRotate(arr, k, n); printArray(arr, n); } } // This code is contributed by Gitanjali. |
Python3
# Python3 program for right rotation of # an array (Reversal Algorithm) # Function to reverse arr # from index start to end def reverseArray( arr, start, end): while (start < end): arr[start], arr[end] = arr[end], arr[start] start = start + 1 end = end - 1 # Function to right rotate arr # of size n by d def rightRotate( arr, d, n): reverseArray(arr, 0, n - 1); reverseArray(arr, 0, d - 1); reverseArray(arr, d, n - 1); # function to pr an array def prArray( arr, size): for i in range(0, size): print (arr[i], end = ' ') # Driver code arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] n = len(arr) k = 3 # Function call rightRotate(arr, k, n) prArray(arr, n) # This article is contributed # by saloni1297 |
C#
// C# program for right rotation of // an array (Reversal Algorithm) using System; class GFG { // Function to reverse arr[] // from index start to end static void reverseArray(int []arr, int start, int end) { while (start < end) { int temp = arr[start]; arr[start] = arr[end]; arr[end] = temp; start++; end--; } } // Function to right rotate // arr[] of size n by d static void rightRotate(int []arr, int d, int n) { reverseArray(arr, 0, n - 1); reverseArray(arr, 0, d - 1); reverseArray(arr, d, n - 1); } // Function to print an array static void printArray(int []arr, int size) { for (int i = 0; i < size; i++) Console.Write(arr[i] + " "); } // Driver code public static void Main () { int []arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; int n = arr.Length; int k = 3; rightRotate(arr, k, n); printArray(arr, n); } } // This code is contributed by vt_m. |
PHP
<?php // PHP program for right rotation of // an array (Reversal Algorithm) /*Function to reverse arr[] from index start to end*/function reverseArray(&$arr, $start, $end) { while ($start < $end) { $temp = $arr[$start]; $arr[$start] = $arr[$end]; $arr[$end] = $temp; $start++; $end--; } } /* Function to right rotate arr[] of size n by d */function rightRotate(&$arr, $d, $n) { reverseArray($arr, 0, $n - 1); reverseArray($arr, 0, $d - 1); reverseArray($arr, $d, $n - 1); } /* function to print an array */function printArray(&$arr, $size) { for ($i = 0; $i < $size; $i++) echo $arr[$i] . " "; } // Driver code $arr = array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); $n = sizeof($arr); $k = 3; rightRotate($arr, $k, $n); printArray($arr, $n); // This code is contributed by ita_c ?> |
Output:
8 9 10 1 2 3 4 5 6 7
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